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