Doubledoom
Whenever the dungeoneering landscape gets a bit crowded, more economically-minded dungeon horrors will share their living quarters with other creatures. Adventurers who wander into the coincidentally-named Doubledoom Crypt often report multiple boss sightings.
Doubledoom is a Hard difficulty dungeon, probably the first dungeon the player will encounter that hosts multiple bosses. It is unlocked by completing the quest Second Generation. The layout consists of 6-8 smaller islands, separated by an underground river with stepping stones, with also some regular walls at the center of each island. The same layout is reused - with different tilesets - for other dungeons, like Dragon Isle and the Sorcerer Gold challenge.
One thing to note about the level's layout is that it often leaves very few valid places for the game to place the secret subdungeon, making it relatively easy to find--it requires a 9x9 square of walls. It will almost always be bordered by at least one wall tile that you can see from outside, so if you examine the center of each island you should be able to find it. Don't convert the 
ENDISWAL glyph until you find it, and consider bringing a 
Transmutation Seal if you have it unlocked.
Overview
Monsters: All unlocked so far. Monster difficulty is 110%.
Bosses: There are two bosses, selected randomly from the available bosses. Both of them need to be defeated to win Doubledoom.
Strategy
Recommended Classes: All
As the bosses in this dungeon are random, it is recommended to keep the strategy flexible, and tailor it to the specific bosses. Classes that are more versatile - like the 
Thief or 
Tinker - are generally optimal for this level. That said, your initial challenge will be to win this dungeon with all Tier 3 classes.
Warlord is probably the easiest, because his ability to more easily go for higher-level kills makes him less picky about choosing opponents. Without wasting too much space on exploration, the warlord can effectively take out the higher level monsters and earn tons of bonus experience doing so. Best monsters for bonus experience: 
Gorgon & 
Goat. Diffult bosses: Super Meat Man (regen-fight, combine melee & BURNDAYRAZ); Tower of Goo & the Tormented One (rely on BURNDAYRAZ for both).
Assassin will only struggle with undead opponents, which is why it's generally good to just out-level them and kill them using SWIFT HANDS. Use poison-fighting against a few key higher-level opponents to gain bonus experience. Best monsters for bonus experience: 
Meat Man and 
Bandit (if you don't mind getting overly cursed). Difficult bosses: Bleaty, the Tormented One (rely on BURNDAYRAZ for both); Frank the Zombie (try to get items that increase your damage and/or resistance).
Bloodmage needs a bit of skill to play well, but is actually one of the strongest of the four given his natural affinity to switch between melee and magic. Best monsters for bonus experience: 
Wraith and Gorgon. Difficult bosses: none; you may need to switch between BURNDAYRAZ + BLUDTUPOWA for the lower health bosses, and Melee + Sanguine regeneration for the lower damage bosses.
Paladin plays really well against physical-damage opponents and shrugs off Poison easily. Best monsters for bonus experience: 
Serpent, Goat and 
Golem. Difficult bosses: Bleaty (rely on BURNDAYRAZ); the Tormented One and Tommy Longfellow (either purchase the Soul Orb, or rely on BURNDAYRAZ).
Quests
The quest associated with Doubledoom is Double Take, during which you must defeat Doubledoom with every Tier 3 class to earn the 
Piercing Wand.
