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