Dota 2 is Valve's stand-alone sequel to the popular Warcraft III mod Defense Of The Ancients. Valve had hired Icefrog (One of the game's original developers) and have been working on a commercial sequel/remake of a sort. It was recreated on the Source engine with all-new graphics and UI. It was released in July 2013 after a lengthy closed beta. Recent updates about Dota 2 can be seen here. For information on professional teams and their members, look under the multiplayer online battle arena folder in Professional Gaming.
The original DotA mod had two factions of heroes to choose from, plus a neutral side, and normally defaults to allowing the Sentinel (Radiant) and Scourge (Dire) to only pick from their hero pools and the neutrals. Completely open picking became ubiquitous in later versions, however, so the formerly neutral pool has been integrated into the Sentinel and Scourge sides. Thus there are True Neutral characters like Sand King on the Dire, and mercenaries like Bounty Hunter on the Radiant.
Backstories of various characters have been changed, in order to avoid references to Frozen Throne, since Dota 2 is set in a separate universe, and Blizzard owns the copyrights to all elements of the Warcraft games, many of which were incorporated into the original DotA. However, even characters whose backstories have been radically changed are still on whichever side they were on in DotA. So, while Centaur Warchief is a heroic saviour fighting for the Sentinel in DotA, his equivalent, Centaur Warrunner, is simply a Blood Knight on the side of the Radiant in Dota 2.
Artificial Stupidity: The bots on your side seem to be retarded, while the enemy bots move and gank together seamlessly. Your bots are more likely to feed the enemy countless kills and making the game impossible for the player to come back from. Some would argue that this mirrors real public matches in Dota.
Ascended Fanboy: Pyrion Flax, a popular YouTube Dota 2 satirist, managed to get his very own announcer pack added to the game.
Ascended Glitch: Several quirks of the Warcraft III engine were intentionally replicated, and several quirks of the early beta have been left intact as well:
Though integral to the game for years, "denying" allied creeps (killing them to deny the enemy the cash and experience reward) was originally an unintended feature.
Creep stacking is a method where a player draws the aggression of neutral creeps to make another stack of them spawn in the same camp at the minute mark, when all empty camps will respawn. Though originally a glitch, this is such an integral part of DotA that removing it was unthinkable.
Although since removed, Valve at one point stated that the technique known as "fountain hooking" would be left in the game. Fountain hooking refers to aggressively teleporting or dragging an enemy into their opponent's fountain, where the high damage will likely assure an Instant Kill. While it's most well known with Pudge and Chen, it was possible with a small handful of other heroes as well, such as second-runners, Magnus and Io, who, on one hand, are even harder to pull it off with, but on the other, are potentially capable of grabbing multiple people and returning to the fight afterwards respectively.
Baleful Polymorph: Lion, Rhasta, and the item Scythe of Vyse can turn an enemy hero into frogs, chickens and pigs, respectively.
Beauty Equals Goodness: The more humanoid, attractive females are all on the side of Radiant. Dire gets the more non-humanoid ones, ambiguous-looking (Mortred) or Evil Is Sexy ones (Akasha). Though the Radiant itself isn't 100% Good mostly and also has its share of non-humanoid ones (eg: Slithice).
Call a Smeerp a "Rabbit": Quite a few characters, mostly with Sniper and the archers; Sniper refers to arrows as "feather bullets" and Windranger refers to Sniper's bullets in turn as "tiny featherless arrows"
Calling Your Attacks: Most Heroes (some of them more than others) often either say the name, effect of, or a slang term for their spells during/immediately after casting them, especially for spells that are used specifically against enemies, so long as they don't just outright taunt the other guy (or make anIncredibly Lame Pun at them) instead.
Tusk will say some variation on Walrus PUNCH! ("x Punch!") accompanied by large red text reading "Walrus Punch!" next to his target every time it's used on a hero. On a creep, he'll say something like "Disappointing punch!" or "Moderately painful punch!" accompanied by small blue text reading "Penguin Punch!" next to it.
Rubick can do this, since he potentially has access to just about every single spell in the game, and it could possibly be taken Up to Eleven depending both on the speed of any given person playing Rubick, and how extensively Valve has recorded/will record additional lines for his stolen spells in the future (as it is already fairly extensive).
Captain Ersatz: Due to certain heroes from the original mod being named directly after Blizzard-trademarked characters or races, some heroes had to be renamed.
Cast of Snowflakes: Every character has unique appearances, abilities, backstories, and extensive responses to certain events. All of them are fill in very different niches in gameplay and team composition, to the point where several heroes' schtick cannot be replicated by another.
Color-Coded Wizardry: Most hero's abilities are colored in a single color, usually the same one as the background of their abilities.
Combat Pragmatist: Split-pushing, or "Rat Dota", involves forcing the enemy team to one location on the map, and then going to the opposite end to destroy their towers and barracks unchallenged. Many heroes (particularly Pushers) such as Nature's Prophet and Broodmother are notable for this. The best counter would simply be to Gank the Split-pushing hero, and repeat as necessary, taking advantage of them being separated from their team to gain gold.
Magnus can potentially suck the entire enemy team into a single compact area in front of him and disable all of them with Reverse Polarity before Sven walks up and uses his high damage and Cleave to dice them all up in seconds while using Storm Hammer a smaller area-of-effect stun to give them more time to beat on their victims and Magnus' Empower gives both of them more damage and Cleave.
Sven and Crystal Maiden compliments each other, which is also the basis of their apparent shipping. Aside the fact that both have skills that keep the enemies at place (Storm Hammer-Frostbite-Crystal Nova) so both can wail on the stunned/frozen enemy (moreso if Sven has activated God's Strength), Sven's mana-hungry problem is migitated with Rylai's Arcane Aura, which increases his mana regeneration (and Rylai being a support hero means that she is also likely to buy Arcane Boots to fill up Mana) so he can throw more Storm Hammers. Whereas Rylai's squishy armor and cumbersome movement speed is also mitigated with Sven activating his Warcry, which increases his and allies' armor and movement speed. With Sven's area stun, Rylai can also have an easier time to set her Freezing Field up.
In terms of setting up Freezing Field, however, Tidehunter does the job better as his ultimate, Ravage, is an AOE skill that stuns everyone in the area, which is perfect for team fights. Tidehunter can also help keeping Rylai's enemies in place by using Gush. However, they don't mitigate each others' flaws as much.
If Magnus's stun is not enough, Ember Spirit could be a very effective replacement, his Sleight of Fist lets him deal massive damage to groups with Cleave, Magnus's Empower being worth more than a Battle Fury and boosting attack damage on top of that, can potentially result in a One-Hit Polykill as all those overlapping cleaves can easily shred through entire teams.
Ursa has effectively nigh-infinite potential damage due to being able to do more damage every attack using Fury Swipes, and almost always successfully uses this to kill Roshan at an early stage of the game. However, he will usually not last long enough without lifesteal effects. Enter Wraith King and his Vampiric Aura which grants all nearby allies lifesteal.
Huskar has an ability that deals 50% (or 65% with an Aghanim's) of the opponent's current health in damage, and Necrophos has an ability that can deal damage to a target based on how much health it is missing (up to around 1-1 damage for each point of health missing). Targets of this combination tend to die.
Huskar's damage is further complemented by Witch Doctor's Maledict, which deals bonus damage every four seconds based on the HP an opponent has lost since the Maledict was cast. If Witch Doctor casts Maledict on a hero with 1500 HP, and Huskar deals 750 damage with Life Break, the Maledict will deal up to 900 bonus damage over time, allowing Huskar to secure the kill even if the target flees. Additionally, both Huskar and Witch Doctor can heal, allowing them to shrug off any damage caused by the opponent during the gank.
Tiny's ultimate makes him bigger and stronger for each level put into it, but with the tradeoff that each one reduces his attack speed permanently. Enter Wisp and its Overcharge ability that gives Tiny just enough attack speed to effectively ignore the attack speed loss.
Tiny and Centaur Warrunner is another popular combo: Centaur's melee-ranged stun and nuke are guaranteed to land when Tiny throws him on top of the target, and can then be followed up by Tiny's own stun.
A little different, but Luna and Night Stalker work fairly well together, as the two of them are among the very limited number of heroes who have long sight range during the night, both of them have ultimates that turn the day into night or extend nighttimenote Luna's is much shorter, only 10 seconds, but could still easily help make the difference, especially in a team fight, and all of Night Stalker's abilities work better during the night.
Phoenix's ultimate Supernova, involves changing into an immobile egg for 6 seconds which deals massive damage per second in a very large AoE, and will stun and give Phoenix back full life, mana, and refreshed cooldowns on its other spells, but only if it manages to last that long. The other team can deal with it by either destroying it with a few auto-attacks (up to only 10 on the last level) which kills Phoenix in the process, or just running away from it. Enter Treant Protector's and Faceless Void's ultimates Overgrowth and Chronosphere, which disable any enemy movement or attacks in a large area.
While not done terribly often in serious games for a reason, it's still possible to stack up multiple heroes who have global ultimates that will be used simultaneously. A lineup of this will likely consist of Zeus, Nature's Prophet, Silencer (with the Scepter upgrade), Spectre, and likely Ancient Apparition (Invoker's Sun Strike could also do, along with a couple other hero's abilities). Results may vary, but hilarity will likely ensue, in one way or another.
Heroes will global abilities also benefit greatly when they have Bloodseeker in their team. If an enemy is wounded pretty badly, Bloodseeker's Thirstwill always reveal their location, enabling these heroes to properly set up their global abilities to ruin the day of the wounded enemy.
Techies has Suicide Squad, Attack! which deals so much damage (650 composite damage!) that it can one hit kill most enemy heroes in a single explosion at level 1, often resulting in a first blood for Techies. Which is cool, awesome and scary until you realize that Techies has the SLOWEST movement speed of 270, just 10 less than Crystal Maiden, and the ability is activated at point blank range, meaning that he will pretty much never move close enough to get a first blood on his own unless he manages to take someone by complete surprise. Cue Tiny, who can use Toss to throw Techies right on top of some poor victim.
Ironically, Nature's Prophet and Timbersaw can work well together. Timbersaw requires a tree so that he can quickly move around with Timber Chain and/or deal pure damage with Whirling Death and hopefully catch fleeing enemies or escape them, which becomes difficult in open areas or places where Timbersaw has already cut down most of the useful trees. Nature's Prophet is capable of spawning trees anywhere and around an enemy. With Sprout, Nature's Prophet can either help Timbersaw catch and kill his prey or help him escape from enemies, which is easily done with Teleportation.
Complete Immortality: Four characters (Keeper of the Light, Enigma, Chaos Knight, and Wisp) are "Fundamentals": beings from the beginning of reality that are ageless and impossible to truly kill. The Radiant and the Dire are also Fundamentals, ones that were cast out by the others for constantly feuding.
Conservation of Ninjutsu: Potentially played straight. When a player abandons a game, the gold-per-second they earn is split between their teammates, and so is the gold their hero possesses. Certain heroes who rely on items to carry benefit massively from this (for example Faceless Void, Phantom Assassin and Phantom Lancer), especially if three or four teammates abandon, and can within a few minutes acquire powerful late-game items, allowing them to effectively take on entire teams solo, where otherwise they could only do so after an hour of farming.
Continuity Reboot: The original DotA never had much of a story past minor hero and items descriptions, and for the most of it used lore already established in Warcraft as a base. With the remake being developed by Valve, they couldn't obviously use anything relating to Blizzard products. This gave them the chance to completely clean the slate and create their own fantasy world, giving all the heroes completely new and original backstories, though still using the original DotA heroes as a base.
Crutch Character: Certain support heroes like Earth Spirit and Chen. They are especially powerful early game when enemy heroes haven't yet acquired many items, but their lack of scaling means that they'll fall off rapidly late game when the enemy can catch up.
Death of a Thousand Cuts: Many heroes have area-of-effect spells that don't do very much damage to single targets at all, or have auras that don't do a lot by themselves. The difference comes when you stack those spells and auras with those of the other four players on your team, which can quickly grind down even the hardest carries in the game under the right situation. That makes tactics very important to players.
Death Ray: The Dagon's active ability Energy Burst, which fires a beam that deals instant magical damage to the target.
Dem Bones: The Dire has quite a few undead heroes.
The Dev Team Thinks of Everything: Valve had every voice actor do a line for purchasing an Aghanim's Scepter, even heroes whose ulti couldn't be upgraded. Loads of heroes have had ultimate upgrades added since the lines were recorded.
Dynamic Entry: Blink Dagger and Force Staff, two moblity items often built by heroes with short-ranged abilities to get into position easier.
Everyone Calls Him Barkeep: The game calls most heroes by their titles instead of their proper names. This spreads to the player base as well. It's easier to count which heroes that avert this. note Sven, Tiny, Kunkka, Huskar, Io, Elder Titan, Mirana, Riki, Luna, Puck, Zeus, Lina, Jakiro, Chen, Rubick, Pudge, Slardar, Undying, Magnus, Abaddon, Razor, Viper, Clinkz, Meepo, Slark, Medusa, Terrorblade, Lion, Pugna, Dazzle, Leshrac, Visage, Disruptor
Evil Laugh: Very prominent. Almost every hero has a response of this sort to killing an enemy hero. Oddly, in this game it doesn't produce any Narm feelings, because whoever just scored a kill will usually feel like a badass, so if you get the laugh response it just makes the experience better.
Gender Flip: Tresdin the Legion Commander. In DotA he was a male, horse-riding, mustachioed, racist to non-humans, commander of a legion. In Dota 2 he has become a woman with somewhat darker skin who fights on foot. The racism is toned down, but she is still somewhat aggressive towards non-humans, especially demons after Stonehall.
Additionally, Auroth the Winter Wyvern has also been confirmed for a gender flip as she shares the same voice actor as Tresdin.
Genre Shift: The various holiday events all deviate from the standard 5v5 Ancient-destroying gameplay.
Both the 2012 and 2013 Diretide events are Capture the Flag competitions that segues into a 10-on-1 fight against a buffed Roshan.
The 2012 Greeviling event was a race between both teams to kill as many Greevils as possible in a set time limit.
The 2013 Wraith Night event was a 5-man Tower Defense game where five heroes defeat waves of monsters and heroes for 13 rounds.
The 2014 New Bloom event pit the team against the Year Beast. Slay it and you can get loots for cosmetic item crafting. The most damaging players got a VERY rare Jadehoof courier.
There are too many Incredibly Lame ones to count (although, impressively, it almost never diminishes the overall experience):
Lich (casting Ice Armor): What's a little frost among friends?
Faceless Void: In the land of time, the no-eyed man is king.
Chaos Knight: Armageddon out of here.note Although Armageddon is also the name of his horse
Outworld Devourer: Good news travels slowly. Bad news has wings.
The blog update for Bristleback says:
Better watch your back, because Bristleback is back! (kill me).
Homing Boulders: It's possible for autoattacks and spells to change direction in midair and fly across the map if the targeted hero teleports away or moves away very quickly. This is especially ridiculous with some characters, like Sniper, whose bullets can spin right around in midair to chase their target, or Tiny, whose Toss throws a nearby unit to a target enemy, even if the Toss trajectory makes no sense and bends around in the air. It also gets absolutely ridiculous with skills such as Huskar's Life Breaknote he leaps at an enemy for massive damage, where Huskar actually changes direction mid-air if his target blinks away, even if the target blinks behind Huskar.
Taken Up to Eleven with Io, whose ultimate is a global teleport. However, it doesn't disjoint projectiles, so if a ranged hero throws an autoattack that doesn't connect before Io teleports, the attack could potentially fly all the way across the map, giving the Io player a nasty surprise.
Immunity Disability: It's usually a good thing to cast Magic Immunity on yourself in the middle of battle to prevent the enemy from stunning you - but this also prevents your allies from casting healing spells on you.
Instant 180 Degree Turn: Averted. "Turn time", or the half-second pause that a hero takes to turn to another direction of running, is an important gameplay mechanic to get used to and one of the balancing factors for melee vs. ranged heroes to ensure that the latter can't just kite the former with complete impunity.
One of Batrider's skills actually increases the turn time of whoever he uses it on. Good luck kiting at all.
I Shall Taunt You: Certain characters have specific, mocking lines when killing other heroes. Some even have dedicated taunt animations that can be executed on command if you own the item in your backpack. Axe even has an in-game ability for this too - he magically taunts his enemies and forces them attack him so they cannot attack his (usually easier to kill) allies, and placing the enemies in position to be hit with his other ability, Counter Helix.
Since the damage output for casters comes mostly from their burst-damage nukes, they tend to be powerful early game when enemy heroes have few items; but because nuke damage generally do not scale with items they fall short later when enemies become able to shrug their nukes (and their weak auto-attacks) off.
Compare to physical damage dealers, who rely on right-click auto-attacks enhanced with passive abilities: their damage early on is weak, but scales very well and becomes stronger and stronger as they acquire more and more items, and in the late game they become major nexuses of power.
Some heroes, like Shadow Fiend, Gyrocopter and Skywrath Mage are powerful all game due to heavy nukes and good scaling into late game.
Magikarp Power: Hard carries like Medusa or Anti-Mage start the game very weak, spend most of their early- and mid-game farming incessantly and watching out for ganks, but are the strongest heroes late game, able to 1v5 whole teams by themselves if properly farmed.
More Than Mind Control: Non-heroes exposed to Direstone or Radiant ore quickly become warped by it and turned into creeps. This is ultimately reversible, though not without extreme effort.
Money Multiplier: Hand of Midas, Maelstrom, Battle Fury and Radiance. They are often not particularly effective in combat compared to other similarly priced items, but they can massively boost the farming speed of their owners.
Monster Allies: Chen and Enchantress can turn neutral creeps into their loyal followers. The Helm of the Dominator extends this capability to everyone with its active Dominate.
Ms. Fanservice: On whole, averted. While some humanoid heroines ARE attractive, they're not overly sexualized to the point of fanservice.
Mythology Gag: If you look closely at the icon for item recipes, the icon in the middle is the symbol of the Combine from Half-Life 2.
Stealth Pun: ...Because you use recipes to COMBINE items.
No Experience Points for Medic: You only get assist credit if you damage the slain enemy. This is why certain melee supports (like Omniknight - most of whose spells protect his allies or slow enemies, or Treant Protector - whose ultimate stops enemies from moving or attacking but does 0 damage) tend to not have great scores since they lack easy damage spells to pick assists up.
However, simply being near a dying enemy nets you gold and experience.
Non-Action Guy: The two Ancients (the Radiant and the Dire) manifest as defenceless buildings that must rely on towers and heroes to protect.
No Sell: One of the biggest mechanics of the game's meta-strategy is that some heroes are complete hard counters to others (such as Omniknight's Repel being able to completely nullify the effects of Slardar's Amplify Damage and many of Spirit Breaker's abilities, but Repel itself able to be purged by a Diffusal Blade), so choosing the correct lineup or item build against the other team can result in this. Again, rewarding good decision makings: turn the tide of the battles even when you are behind, if you are smarter than your foes.
Our Dwarves Are Different: While not outright stated, the Keen (Sniper, Tinker, Clockwerk, Gyrocopter, and the smaller half of Alchemist) share similarities with Dwarves. Most are incredibly smart and sport facial hair, and all are very small in stature.
Perfect-Play A.I.: When playing with/against bots, they will most often perform perfect chain stuns/disables, on the level of pro players.
Power Creep: This is often a large factor in what determines the meta in competitive gaming. Heroes that don't get nerfs in certain patches (or even actually get buffs) can find themselves retired from the meta simply because a buff elsewhere created a better option in another hero.
Randomized Damage Attack: Chaos Knight has Chaos Bolt, which inflicts a random but inversely-related amount of damage and stun. Upgrading the spell increases both the maximum and minimum values of both the damage and stun, but there's still a big difference between a 275 damage skill that stuns for 2 seconds, and one that does 100 and stuns for 4.
Revenue Enhancing Devices: Despite the fact that the game is completely play-for-free from the get-go, and you play as every hero from the start, the online store still manages to have a ridiculous amount of purchasable-with-real-money content. With the exception of tournament tickets (which allow you to spectate international tournaments from in-game) though, all of these store items are only cosmetic in nature, a vast number of them can be obtained through Random Drop as above (with even some only being available through drop and not through the store), and none of the availability of the game itself is locked away. An exception to the tournament ticket rule goes to the annual "The International" tournament held by Valve. You can watch the in-game matches for free, and Valve makes money by selling "See it live" tickets and (for the 2013 tourney) the Compendium which is $10 for at least $35 worth of content and a promise for more as more Compendiums are bought.
Rivals Team Up: While every playable character in the game is listed as being on either the Dire or Radiant side, this has no bearing on which team they end up on when a match starts; Anti-Mage, for example, can end up on the Dire team. So anybody can be teamed up with anybody else, pretty much, even if the lore says that two characters hate one another's guts. Sometimes when this happens the two rivals will have mean things to say to one another, but will still work together.
Frostivus 2013 Day 2: BY DECREE OF THE ONLY KING THAT MATTERS - FROSTIVUS IS CANCELLED
Every heroes have a taunt voice-set, but all of them will be about "It's in the bag!". Also each heroes have a quote to curse about the "Shitty/Crummy Wizard!". Some heroes can say it straight, some gets Sophisticated as Hell about them.
Ryu and Ken: As in the Original Dota, players could only pick Sentinel or Scourge (renamed Radiant and Dire for Dota 2) heroes when on that side, alot of them were largely equal to eachother, such as Lina and Lion, Sven and Magnus, Omniknight and Abaddon, and others. Divergent Character Evolution has completely changed most of these heroes (Magnus and Sven don't even fall into any of the same roles anymore).
Schizo Tech: Several of the Keen (ie, the Gnome analogues) have incredibly advanced technology, Tinker even having lasers, rockets, and automonous robots. They exist alongside and are routinely beaten by people using arrows and swords. However, Gryocopter's backstory mentions finding an "incomplete schematic for a Gyrocopter, the world’s first manned, non-magical flying device". So, while technology, with the help of magic, is incredibly advanced, pure technology is mostly inept.
Shout-Out: Just as with the original, with the sheer number of assets in the game, most anything is a reference to something else:
A red headed spellcaster named 'Lina the Slayer' with the skill Dragon Slave, and an ultimate named Laguna Blade?
Beating the newly resurrected Wraith King shows the words YOU DEFEATED.
Sinister Surveillance: A particularly vital concept in the game is warding to gain vision of key areas, and denying enemy vision of key areas.
Skill Gate Characters: Quite a few heroes are inherently imbalanced in the lower brackets, where they are able to exploit and punish mistakes often made by new players: do not buy detection (Riki), do not carry TP scrolls (Bloodseeker, Viper), no wards (Spirit Breaker), play too passively early game (Drow Ranger, Riki, Sniper, Viper), can't control creep aggro (any orbwalker), or do not adjust an item build to counter an enemy hero (Zeus).
Socketed Equipment: Cosmetic items can be socketed, for gems which give special cosmetic effects.
Standard Status Effects: Poison damage, paralysis, stuns, slows, and silences are invaluable in teamfights. Several heroes (Venomancer, Viper, Silencer, Bane, Lich, and Spirit Breaker, to name a few) are themed entirely around a specific status effect.
The Diffusal Blade's active ability and the neutral Satyr Banisher's abilities both named Purge, which purge most negative buffs from allies and positive buffs from enemies in addition to slowing them.
Shadow Demon's Demonic Purge is a variation of the above, being useable only on enemies but also deals damage and able to remove certain buffs that the normal Purge can't.
Stop Poking Me: In addition to unique lines being stated from clicking on your hero repeatedly ("rare" responses), they'll also get irritated from you trying to cast an ability on cooldown or without enough mana for it repeatedly, or from the game's pause lasting too long.
Suffers Newbies Poorly: As with many other games in the MOBA genre, gameplay is extremely serious business, and new players are often subjected to an incredible amount of vitriol. The developers have tried to alleviate some of this by introducing a tutorial mode, but it's a long and steep learning curve no matter how the game is played.
Summon Magic: Certain heroes have the ability to summon minions that range from expendable (Broodmother's spiderlings) to very valuable (Visage's familiars). The Necronomicon allows all heroes to do this with its active ability Demonic Summoning.
Talking Is a Free Action: Characters regularly banter with each other. Heroes will comment on loads of events, including buying a specific item, calling misses, killing certain other heroes, meeting certain allied heroes, getting a cosmetic item at the end of a game, and getting banned during the ban/pick process in Captain's Mode. Taken to ludicrous extremes with Storm Spirit, who takes this up to Lull Destruction.
Team Spirit: Teamwork and Communication trumps nearly everything else, a properly co-ordinated team will usually beat one with a higher APM because while their enemies trip over eachother and blaming eachother for any mistakes, they'll be comboing their abilities, and keeping eachother updated on possible enemy gank attempts.
Touched by Vorlons: Several characters have abilities conferred by beings greater than themselves.
Unexplained Accent: A good majority of the heroes are outfitted with various accents despite not being in the real world.
Anti-Mage, Invoker, and seemingly Axe speak with light English accents. Pudge speaks with a more thick urban English accent, as does Bristleback.
Mirana speaks with a light Greek accent.
Meepo's accent sounds somewhat like a typical Brooklyn accent.
Luna has a very thick Irish accent.
Death Prophet has a very thick French accent, while Phantom Assassin has a more subtle one, perhaps French-Canadian.
Slark has what sounds like an Australian accent.
Through her echoing voice, Medusa sounds like she has a high class English accent, or an older American accent, like one from the 1940's -1950's.
Chaos Knight has a deep voice, but he appears to have a German accent.
Dazzle has a Mali accent.
Magnus has an Ethiopian accent.
Witch Doctor has a Rastafarian-type accent.
Bloodseeker sounds like he has a Central American Accent to go with his 'Sacrificial Tribal' Theme.
Shadow Shaman has a Persian accent.
Sven and Tusk have Swedish accents. Sven sounds more like your typical Viking where Tusk sounds more like a Modern Swedish Accent.
Brewmaster and Juggernaut have Japanese accents.
Lone Druid has a Scottish accent.
Skywrath Mage sounds Middle Eastern.
Lycan seems to have a Slavic accent.
Updated Re-release: The game is more or less a direct clone of the original Defense Of The Ancients All Stars map from Warcraft III, but has a new engine, brand new graphics and a modern interface. Several characters work differently because of the new engine, as the old Warcraft III engine put restrictions on certain spells. Rubick can steal transformation skills (most notably Elder Dragon Form and Shapeshift), and Luna's Moon Glaives work differently.
What the Hell, Player?: Attempt repeatedly to use an ability when it's on cooldown or you don't have enough mana, and your hero will sound more and more agitated/annoyed with your rapid clicking. Troll Warlord especially hates it when you do that.
Riki, a character whose defining characteristic is being invisible nearly constantly throughout the game, either sounds very confused or gives a snark reply about redundancy when he picks up an invisibility rune.
A Wizard Did It: The accepted canon behind any bugs encountered within the game is that a particularly shitty wizard is mucking around with the battlefield.
World of Ham: Every hero, even the most subdued (but not The Speechless), will mock enemies they kill and laugh when they score multi-kills. Also, many heroes will utter a hammy line when using a skill.