Here is the full list of all 9 The Sink Gods achievements.
Play the game as Robin
Play the game as Gwendolyn
Complete all the puzzles in The Temple
Complete all the puzzles in the Temple of Knobus
Complete all the puzzles in the Temple of Spoutus
Complete all the puzzles in the Temple of Drainus
Become Garbulator and gain vengeance.
Start Aftermath
Complete Aftermath