Here is the full list of all 39 Cathedral achievements.
Complete the game without upgrading the armor
Have more than 50 000 gold stored in the bank
Destroy an electric orb in Necromancer's den using the lantern
Die one hundred times
Kill Ardur
Find all ammo upgrades for the Magnus Apparatus
Find all ammo upgrades for the Flintlock
Find all armor augmentations
Find all map pieces
Destroy the Conduit
Find and activate all portals
Acquire all Ouroboros amulets
Slay all gargoyles
Kill the blood knot
Acquire all health bottles
Return 100 books
Return 80 books
Kill Oloc
Kill Nidlong
Find all hearts
Find all charms
Buy the Onyx armor
Kill Thalia
Buy the Tourmaline armor
Return 60 books
Have more than 25 000 gold stored in the bank
Kill 150 blobs (of any kind)
Kill 150 skulls (of any kind)
Kill Salemacke
Return 40 books
Have more than 10 000 gold stored in the bank
Kill the Necromancer
Kill 100 skulls (of any kind)
Return 20 books
Kill 50 skulls (of any kind)
Kill 100 blobs (of any kind)
Buy the Emerald armor
Kill Augr
Kill 50 blobs (of any kind)