The new 0.2 version of Desktop Dungeons has a new special level called the Boss Hive. The special feature of this dungeon is that it includes all possible monster types, and all monsters (regardless of level) are given the same bonuses that the boss monster of that type gets. This means extra damage, extra hit points, and extra special abilities.
In order to unlock the new class in the 0.2 version, you need to beat Boss Hive with 4 different classes. So which classes are best suited to this environment?