Here's the chambers of the Everfall and what you'll find inside:
0. Confusion - mandatory, any door you enter will bring you here. Evil Eye.
1. Anxiety - Lich, Undead, Skeletons.
2. Absence - Inky Saurians, Magi, Hellhounds, Grim Goblins.
3. Hesitation - Snowy Saurians, Undead, ArchHydra.
4. Apprehension - Gore Chimera, Wights, Undead / 2 Cockatrices, Grim Goblins, Vile Eyes.
5. Remorse - Grim Goblins, Golem, Cyclops, MERCHANT.
6. Tragedy - Succubi, Gargoyles, Phantasms.
7. Lament - UR-DRAGON
8. Fate - Drake + Harpies or Chimera + Gore Chimera + Lich summoning Hellhounds / Succubi, Gargoyles.
9. Distress - Direwolves, Snow Harpies, Wyrm.
10. Estrangement - Golem + Cyclops + Ogre or Metal Golem + Wight / MERCHANT, Undead, Phantasms.
11. Woe - Lich, Fell-Lords, Undead.
12. Sorrow - Tentacles, Vile Eyes, Grim Goblins, Evil Eye.
13. Resolution - Ogres, Undead, Cockatrice, Inky Saurians.
14. Inspiration - Phantasms, Magi.
15. Hope - Bloated Undead, Hellhounds, Gore Chimera, Magi.
The Chamber of Fate encounter with the Chimera+Gore+Lich+Hellhounds is arguably the toughest fight outside of BBI.