Here is the full list of all 25 The Keep achievements.
Finish tutorial.
Save at least one child.
Save all children.
Finish Chapter 1: Tower Entrance.
Finish Chapter 2: Prison.
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 at least one enemy.
Kill all enemies.
Find at least one hideout.
Find all hideouts.
Find Nataniel.
Use at least one melee combo.
Use all melee combos at least once.
Cast at least one spell.
Cast all spells.
Discover the hidden ALTernate ending.