Awesome Music: The entire soundtrack is comprised of work by Celestial Aeon Project, and some of the tracks are absolutely amazing, but the biggest example has to be Driving The Top Down, the theme of Tempest Peak.
Any enemy who can spam control spells (especially Sleep and Freeze) classifies, as those can stunlock your character and leave them to take (sometimes lethal) damage from everything else in the room. Even if you have some cleansing infusions, nothing stops them from just reapplying the status before your cooldown expires.
The friggin' orc cryomancers! Soldiers, master assassins, blood mages... are all fine, but for Starclan's sake NO CRYOMANCERS!
Luminous/Radiant horrors are immune to and heal from fire, on top of a solid health-pool and a large amount of damage, meaning that any classes relying on fire without resistance penetration or an alternate means of attack are in for a world of hurt.
Worms that Walk are like Radiant horrors except for Blight-damage classes, and are even tougher!
Antimagic units in general for pure mages. They love to use the silence effect and the most powerfuel ones can damage your mana/vim directly, preventing you from casting at all! It's downplayed for hybrid magic/melee classes (who can just beat them to death with pure sword skills) and are a complete non-issue for non-magic classes (such as wilders, psions, and warriors) but are death incarnate for Archmages, necromancers and corruptors who let them into melee range, who have few-to-no options that don't rely on that precious mana-bar.
Master Archers (or all strong archers in general) are also notorious for dishing out tons of damage and being able to pin heroes to the ground.
Lightning Elementals are a nightmare without lightning resistance, as even the lesser versions can hit you for up to 100 damage, and the greater versions have high damage resistance. Did we mention that one early game quest has you fighting a small army of them, in an open area with little cover?
Fan Nickname: "Ogre-Wielding" for the ability for Ogres to use an offhand with a two-handed weapon.
Fridge Logic: Players with high Cunning will be able to realize that the Apprentice Mage who starts the quest to be accepted in Angolwen is in fact Archmage Tarelion, one of the most powerful mages in the world. So why can't he use the Master's Staff of Absorbtion without dying?
He isn't anymore, and in any case, the Staff is an incredibly high-power piece of Sher'tul magitech, the greatest weapon of the Godslayers. The only non-Sher'tul confirmed to have ever safely used the relics of the Godslayers was Linaniil, when she drained part of the power of one of the gods they killed to become her current immortal overpowered self.
Good Bad Bugs: Due to an oversight, you can pick talents that you only qualify due to item boosts. As such, if you stash away stat-boosing times and only equip them when you have level-up talents to pick, you can take ones you normally would not qualify for and still keep them when you take the stat-boosting items off.
Squick: The Orc Breeding Pits, so much so that Darkgod actually had to remove it from the game once it went on Steam. (Well, that's one of the reasons. The other was that its current form was immersion/lore breaking as it could be accessed well before you stumbled upon the Orc subplot)
That One Boss: So many. Bosses are seriously nasty in the early game, but slowly become more manageable over time.
Bill the Stone Troll, secret boss of the Trollmire, although technically an Early-Bird Boss, is a serious stumbling block for new players.
Wrathroot, boss of the Old Forest, has a reputation for jumping out of nowhere and oneshotting characters before they have a chance to react.
Urkis, Urkis, URKIS. This bastard had the ability to freeze you, using up your precious infusions, and hits even harder than the before-mentioned elementals. His true diabolic nature reveals itself in his thunderstorm ability however: it can easily hit you for 100 damage EVERY turn for a good 10-12 turns, and doesn't end when he dies, meaning that anyone without a magical-effect clearing infusion or an excessive amount of health is in for a drawn-out, humiliating death. As a bonus, the quest to reach him is given out at level 16, and you can't reliably expect to beat him until level 26ish!
The Greater Mummy Lord, boss of the Ancient Elven Ruins, can turn invisible, hit for 300+ damage, and freeze you solid.
Your Cursed clone, who is summoned by the boss of the Shadow Crypt, has all your abilities, all your resistances and then some, double your health, and is boss rank while you're only elite rank.
The Chronolith Twins. Hundreds of powerful spells, including the ability to teleport you around the arena, they're constantly on the move, and they're incredibly hard to out maneuver. Melee classes in particular are in for pure hell. It doesn't help that the arena is 80% water, so if you don't have anything that grants you water breathing...
Embers of Rage gives us the Mindwall. Even if you have the special helmet that makes you immune to her domination spells (which you get by clearing an earlier dungeon), she still possesses some of the most powerful psionic spells in the game, has a near-permanent shielding buff that reduces all incoming attacks to little more than Scratch Damage, and she can heal herself.
The Scintillating Caves and Rhaloren Camp are Early Game Hell, as they're full of very dangerous mages before you have the means of mitigating them, and can kill the unwary or unskilled in scant turns. As a bonus insult, they're the staring dungeons for the Shaloren, the staring race with the least health and therefore the most likely to be WTF-pwned in a single round.
The Orc Prides are hell itself. They're filled with dangerous mages of all kinds, hordes of wyrms, are plentifully filled with bosses and elites, and are wide open, preventing players from funneling them into safe locations and forcing you to fight them all at once. Oh, and each starts with an Inescapable Ambush with a boss AND a horde of minions, again with no cover. The cherry on top is that they're filled with vaults, filled with bloodthirsty mobs even more eager to crush you to bits than the orcs!
Any underwater level in general is this: there are very few items that let you breathe underwater or even extend your breath bar, and drowning will kill you VERY quickly once you're all-too-short breath bar is emptied. Mercifully, all except the Temple of Creation and the underwater caves have underwater bubbles to use, which still isn't enough to save them from this status.
The sandworm caves are really annoying, mostly because progression is limited entirely by the sandworms you have to follow around, making progression slow and boring, and the collapsing tunnels are a very good way to get yourself killed stupidly.
Embers Of Rage contains examples of:
Game-Breaker: In a game where 90% of prodigies are Purposely Overpowered and the other 9% are Overshadowed by Awesome, the remaining 1% is made from the Pain Enhancement System. On a critical hit (trivial for any melee class at this stage) it adds half your strength to every other stats for a few in-game turns: in of itself very useful due to (literally) making you slightly better at everything. However, it can also be accessed by classes that have strength as a secondary or tertiary damage stat. On arcane blades, brawlers, marauders and similar classes, the PES will MASSIVELY up your damage on top of making you nigh-unkillable and indefatigable, making it the top pick. It even synergises with similar Prodgies like superpower and arcane might, skyrocketing damage even further! As a final insult, it also increases your crit chance, making it simple to stay in PES mode!
Earlier versions contain examples of:
Demonic Spiders: The Floating Eye, an early game monster that can instantly kill you if you move into its melee range, due to the tendency for most players to play with Berseker / Running on, making them extremely vulnerable to it's attacks. Worse still, they have a tendency to spawn RIGHT outside of viewing range, meaning you'll turn a corner or use the automated run-down-hallway buttons and end up right in front of their face.
Game-Breaker: Lots in the 2.X series, considering the sheer number of class / race / subrace combos. Some particular standouts:
Summoning — a skill that allows you to create monsters based on bits of their corpses. Where it becomes broken is that Summoned monsters can summon monsters or breed into new monsters. Which means a summoner can summon 1 or 2 White Rats, or perhaps 1 or 2 Great Wyrms of Power, and let the resulting army clean out the map.
Necromancers — Doesn't seem overpowered, until you realize that hacking a monster into 50 pieces counts as 50 different monsters for the Raise Dead skill.
Possession — a skill that allows you to switch bodies with a dead monster. All the exploits of summoning, only now you control when they get used, not the AI. In addition, there are certain bodies such as The Watcher In The Water, which give you the ability to wield an absurd number of weapons at the same time, or a Great Wyrm of Power, which are normally That One Mook, but now under YOUR control.
Alchemy — While Alchemists are extremely weak early on, they get the ability to turn gear into items that are beyond anything else in the game, with a LOT of work. Ultra high end Alchemists can literally make themselves immune to all damage, able to move faster than the gods, attack dozens of times a round, etc etc.
Goddamned Bats: Literally. Fruit Bats move just fast enough that a melee character can't catch them, and do nothing other than interrupt your resting and movement. Later variants are just as annoying, with the added bonus that if they see you with low HP, they'll dive in for the kill — and suddenly the absurd movement speed is a lot less annoying and a lot more scary.
, the theme of Tempest Peak.