As of patch 2.0.6. an alternative avatar named Helga Hammerstorm can be acquired.
And then at patch 2.6.21 a new heroine—not an alternative avatar—got added in the roster... named Solstice. This is her◊, with and without armor.
After the End: According to the Excuse Plot outlined in the "Savage" games, modern day civilisation had it's downfall ages ago and in the far future humanity is once again on it's rise to power but is no longer the single dominant species on the planet as the beasts of the land had evolved and become intelligent. Or, rather, it was going for dominance until the Hellbourne started their onslought at which point it became a battle for survival and an alliance of convenience with the Beast Horde was formed to fight the daemons.
Jesse Cox of OMFGcatavoices "Spiriticus", a (male) alternate skin for Nymphora.
Captain Ersatz: The game itself is a replication of DotA, updated to a much more flexible engine and with lots of online multiplayer convenience. Those days it's split off much more from DotA and has established its own metagame and many different heroes.
Crosshair Aware: Scout's Marksman Shot and Flint Beastwood's Money Shot will put a bullseye above his target while he's charging the ability.
Damn You, Muscle Memory: Try pressing Alt+QQ in HoN. Then switch to DotA and do it again. Plus, spells in HoN all have QWER as hotkeys, rather than varying from hero to hero. So even if your favorite DotA hero happens to be in HoN as well, chances are the initial hotkey confusion will throw you off.
Rather, if you're switching from HoN back to DotA. For those coming from the mod, standardised hotkeys are a godsend. Of course, you can change the bindings in-game, so its pretty much averted here.
Dark Fantasy: A setting where the Legions of Hell is marching towards humanity and beastmen? Check. Weapons at the store that are mostly created by the forces of Hell? Check. Being forced to kill your own men? Definitely a Dark Fantasy setting.
The game itself is Dark and Edgy in general, unlike the lighthearted League of Legends. The heroes will be more than glad to kill their own if they need to and the game has the feeling of a Dark Fantasy.
Bladeknight5: Probably the biggest thing for me when I started playing Ho N, was that I got distracted by all the shiny graphics, I'd be like "Woah that spell is really - CRAP I'm dead." and my team would be like, "Why'd you sit there?" and I would be like, "Ummm... Lag?" 
Dual Wielding: Blacksmith with his dual hammers, the Dark Lady with two katars, Madman with a pair of claws, and Swiftblade with his dual katanas. The recently added hero, Flint Beastwood, uses dual shotguns.
The items Firebrand and Frostbrand can form Frostburn.
Dueling Games: With League of Legends to some extent, but much more so with Dota2. Ho N did less to differentiate itself from the original Dota than League did, so with Dota 2 being similar, with improvements on the multiplayer experience that was one of Ho N's biggest selling points, players have been migrating en masse to Dota 2. This has happened even with some of the pro teams, most notably Fnatic making the jump to Dota 2.
Enemy Mine: When the Hellbourne threw down, the Human Legion and Beast Horde ended their war and joined forces to fight against the demons.
Magebane is allowed to help fight against the Hellbourne - if not for the war, the priests of Sol would have burned Magebane at the stake as a heretic.
Also, Prisoner 945 is well... a prisoner from the dungeons of The Legion's capital, who was imprisoned for leading the rebellion of the Titans. He was released to give Legion another hero that will fight for them, with his chains on him still intact; promising him freedom from the chains if he does well in their fight against the Hellbourne.
Evil Chancellor: Pestilence was once a chancellor to Moon Queen before joining the Hellbourne for power.
Expy: Being an update of DotA, a lot of the heroes have DotA counterparts. Some are fairly obvious (Moon Queen ~ Luna Moonfang, Pyromancer ~ Lina Inverse, Soul Reaper ~ Necrolyte, Keeper of the Forest ~ Treant Protector), but others (Plague Rider ~ Lich, Pharaoh ~ Clockwerk Goblin, Pestilence ~ Slardar, Rampage ~ Barathrum, Witch Slayer ~ Lion) are a bit more subtle.
Myrmidon is an expy of the infamous Magikarp from Pokemon
"Myrmidon uses Taunt on newbie." followed by "It's super effective!"
made even funnier when you realize gyarados frequenly used Taunt
The Blood Hunters left the Beast Horde for the Hellbourne, knowing that they'd be able to drink more blood serving the demons.
Corrupted Disciple once was a priest of Sol, before he was, well, corrupted, and joined the Hellbourne to serve their unholy energy instead of Sol's light.
Demented Shaman betrayed the Beast Horde after gaining access to their holiest secrets to join the Hellbourne.
Forsaken Archer, in life, was a woodland huntress. After being raped and killed by a spurned suitor, she was revived by the Hellbourne to carry out her revenge on the men of Newerth.
Hellbringer, a warlock addicted to demon magic, left the Legion to join the Hellbourne and became the most despised man on Newerth.
Maliken, once the grand leader of the Legion, mysteriously vanished one day. He later reappeared as a mindless, demonic slave to the Hellbourne.
Pestilence once served the Moon Queen, but after realizing that he could never become ruler, he left the Moon Warriors for the Hellbourne and a chance at power.
For a time, Glacius was in the Legion. In more Recent times, however, he has been switched over to the Hellbourne.
And then he pulled a Heel-Face Turn and is now back in the Legion. (as of patch 2.5.7 Glacius is a Hellbourne Intelligence hero.)
Myrmidon was in the Legion for a few months, but once someone found out he was a kind of water deamon, he joined the Hellbourne.
Fake Difficulty: A complaint brought up fairly often about the game is that the shop grid layout and user interface are unnecessarily complicated.
The shop UI was remade to be more user friendly, but some think that it was made less user friendly, although those complaints died within a week or two of it's introduction when people got over the whole They Changed It, Now It Sucks thing.
In a Single Bound: Chronos's Time Leap, Predator's Venomous Leap, and Valkyrie's Courageous Leap.
I Need A Drink: Engineer says a variation of this if you give him a move order.
Instant Armor: The items Astrolabe and Plated Greaves, Arachna's Harden Carapace, Demented Shaman's Storm Cloud, Hammerstorm's Galvanize, Jeraziah's Sol's Blessing, Keeper of the Forest's Nature's Protection, Plague Rider's Cursed Shield and Predator's Stone Hide all give armor at the click of a button.
Instant-Win Condition: World Tree/Sacrifical Pit destroyed? Game over, no matter how many enemy heroes you and/or your team shredded.
Invisibility: Scout can Vanish, Night Hound has Invisibility, Keeper of the Forest can Camouflage himself or his teammates, Madman can Stalk in the shadows, Fayde can activate Reflection, and the item Assassin's Shroud will cloak the user when activated.
Item Crafting: Maintained from DotA. You can combine base items into more-powerful items using recipes. There are well over five dozen recipes.
It's Up to You: Solo mid gankers generally control the game up until lategame, where they pass the reins to the team's carry who will seal the victory almost singlehandedly.
Linear Warriors, Quadratic Wizards: Inverted. Nukers (wizards) are very powerful from early to mid, quickly dropping off during mid- and late-game. Carries (warriors) tend to be very weak early game, eventually becoming a monster late game, killing heroes in 2-3 hits.
Standard Status Effects: This game has a lot of possible status effects, so naturally a few of them match up. Slither's skills cause poison, Pyromancer's Fervor causes burning, a number of heroes have ways of silencing, Blood Hunter's Blood Craze is essentially berserk, Glacius's Ice Imprisonment freezes, Maliken's Possession fears, and there are quite a few slows and stuns in this game.
Suffers Newbies Poorly: Most of the community actively push new players away. In this game, you getting killed does not just hurt you - it helps your enemy, as they make progress towards leveling up by killing you, so a newbie that dies more than average can actually be a net loss to the team. Experienced players know this, and will vote-kick, or cuss out, newbies, to make them leave. Overall, the incentives are structured such that newbies are a liability and experienced players seek to push any on their team out of the match, either by harassment or simple vote-kick.
The announcer and the game even mocks the player for poor playing skills ranging from saying "TOO BAD" for whiffed skillshots. To Unreal Tournament style killquotes. Heroes of Newerth is a ruthless game and it's setting reflects upon it.
Super Mode: Maliken's Possession turns him into a hulking demon. Hammerstorm can summon up his Brute Strength and triple his damage. War Beast undergoes a Metamorphosis making him (literally) unstoppable. Madman can go Berserk and totally flip out on an unfortunate victim.
Summon Magic: The item Puzzlebox, Forsaken Archer's Call of the Damned, Hellbringer's Summon Malphas, War Beast's Summon Hellhounds, and Wildsoul's Summon Beardulon.
Super Strength: When Devourver kills something be it Mooks or Heroes, with a passive skill he gets strength each time until finally it goes over 200, which is bascially saying "HAHAHA now i kill you good".
Teleport Spam: Accompanied by sword slashes when Swiftblade triggers his Swift Slashes.
This is called 'snowballing' and it is only true on team level. Individual heroes that perform well during the early game are useless 30 minutes later and vice versa. However, if there is just one bad player on your team who keeps dying, the game is lost no matter how good the rest of your team is.