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