YMMV / Avernum

• Anti-Climax Boss: Rentar-Ihrno's final battle in the fourth game: to reach her, you have to navigate a field of deadly pylons, kill an Haakai (a powerful demon boss), enter a fortress with plenty of though battles and minibosses and fight through a trap-infested corridor (whose traps can be deactivated by fighting the minibosses) and go through two hard compulsory battles against a ridicolously though Vanhatai Lord and later a Lich which almost-costantly mind-controls your party. If you took a couple of preparations though ( such as obtaining the Shade Shard, then the final boss is suprisingly less resourceful and though than all the previous challenges, most of the danger coming from summons.
• Big-Lipped Alligator Moment: Giant Intelligent Friendly Talking Spiders. The in-game narration will briefly consider the possibility that you've just gone insane. At least one proposes to you.
• Demonic Spiders:
  • Several things are there to ruin your day, including slimes that split into two whenever you hit them. Then there's the Doomguard, which is a boss monster that splits into two whenever you hit it. On normal difficulty, it's just a very long fight that saps every resource a party has. On higher difficulties, Save Scumming is highly recommended.
  • Chitrachs deserve special mention, not because they're all that tough compared to Doomguards, but because the Eastern Gallery in the fourth game was made into That One Level purely by their presence. (To be more specific, more than two hundred of them were present.) And chitraches tend to be near null bugs, a creature who can render mages/priests useless with the terrible act of... being close to them. Yeah.
  • Expect most monsters in the latter third of the game to have upwards of 30-40% chance of parrying or riposting all incoming damage.
  • Spraying Shrubs don't attack directly, but spray the entire party with acid every turn. You tend to encounter several at once, so it can take several turns to get rid of them all. Meanwhile, it's easy to die without even realizing how fast you're dying.
  • Gazers got a huge buff in the remakes. In the original trilogy, they were not so powerful by themselves and just spamming Mana Burn rays at the long range. Though in the remakes, they have become nasty Demonic Spiders that are harder to kill than even some bosses or end-game Mooks.
• Game-Breaker: In Avernum 3, the Radiant Slith Spear can be found at the beginning of the game as soon as the party can afford to buy a boat in New Cotra and can defeat a single Shambler. It's a 1-handed weapon that deals 6-36 + 1-6/lvl in damage on top of granting +1 Pole Weapons and +10% Fire Resistance, making it more powerful than the 2-handed endgame polearms of Avernum 2.
• Goddamned Bats: The gremlins. They're not tough, not very fast... but their only ranged attack is a confusion ray. And they also run away while everyone is confused. To make it even more frustrating, in the original trilogy, they attack twice a round, almost always come in large groups, have no variation in their strategy, and confusion can make a character skip their turn, so 90% of the fight is just waiting for them to finish their attack animations.
• Good Bad Bugs: The first three games use a reverse form of Fight Woosh to put your party back into formation after a battle. If you're already in formation, your group may be moved forward a few tiles, potentially bypassing an event scripted to occur when you step on a tile.
• It's the Same, Now It Sucks!: Avernum 4's plot falls into this category for some.
• Les Yay: Two female NPC's from the town Cotra (and New Cotra in A3), Elspeth and Nance, run an arms shop together and they are in love with each other, which is the sole reason they got banished to Avernum. Even the sign in front of Elspeth's shop in A3:RW says it has a rainbow design (the symbol of LGBT) around the edge.
• That One Disadvantage: Two of them, actually—Cursed at Birth and Completely Inept.
• That One Level: Avernum 4's Eastern Gallery manages this entirely through Demonic Spiders, giant insects known as chitrachs. They're fairly hard to hit, they have high HP and damage resistances, and every time you perform a melee attack on them they have a chance of blocking and damaging you. Oh, and there are 227 of them out for your tender flesh. Enjoy!
  • If you thought the Eastern Gallery was bad, wait until the outside of Khoth's Library at the end of the game, where you get regularly swarmed by chitrachs which 1. Now have three attacks on their turn (two is more than enough to stunlock anyone who isn't wearing the heaviest armor possible) 2. Are highly resistance to any form of magic, in a game where Linear Warriors, Quadratic Wizards rules supreme. 3. When they spawn, they completely surround you, and you have to fight 6+ at a time.
  • The Spiral Pit in 1/Escape From the Pit. It lulls you into a false sense of security by siccing low to mid level undead at you, but halfway through the dungeon, the lights go out, severely limiting your vision and maneuverability, you have to fight through half a dozen Stalker Wights, and the last fight of the dungeon is against Ghosts that can do over 100 damage in a single attack.
  • The Slith Fortifications from the same game(s). On paper, it doesn't look so bad, just a bunch of Slith flingers, mages, shaman, warriors, their pet lizards, and their chieftain. The problem? There are a ton of them, moreso than most of the other Slith dungeons you've been to thus far. Not only that, but the map itself is ridiculously small and cramped, meaning that it is very, very easy to aggro literally the entire fort if you don't know what you're doing.
• That One Attack: You will learn to dread enemy mages' Daze and Lightning spells, as well as enemies that know Control Foes.
• They Changed It, Now It Sucks!: Many fans felt this about the engine switch the series underwent for Avernum IV through VI. Also a case of They Copied It, So It Sucks!—the later games are nicknamed "Averforge" for their similarities to Geneforge.
• Ugly Cute: The friendly spiders. When you click on them to talk with them, there's a voiceclip that says "Hello!" or "Hi!" in a high-pitched voice.