Here is the full list of all 25 The Keep achievements.
Finish game on permadeath.
Finish Chapter 10: Watrys’ Tower.
Finish game on hard difficulty.
Kill all enemies.
Discover the hidden ALTernate ending.
Save all children.
Find all hideouts.
Use all melee combos at least once.
Cast all spells.
Finish Chapter 9: Watrys’ Labyrinth.
Finish Chapter 7: Mining Site.
Finish Chapter 8: Abandoned Mine.
Finish Chapter 5: Dwarves’ Lair.
Finish Chapter 6: Upper Mine.
Finish Chapter 4: Lower Dungeon.
Save at least one child.
Finish Chapter 3: Dungeon.
Find Nataniel.
Finish tutorial.
Finish Chapter 1: Tower Entrance.
Finish Chapter 2: Prison.
Kill at least one enemy.
Find at least one hideout.
Use at least one melee combo.
Cast at least one spell.