Here is the full list of all 14 THOTH achievements.
Finish the main game
Beat 32 levels in a row in coop
Beat the 64 normal levels in one sitting, alone, while in coop-mode (other player must not move or help)
Beat twelve sets of levels
Beat eight sets of levels
Beat 16 levels in a row in single player
Beat four sets of levels
Beat the first set of levels
Beat the set of 8 procedurally generated levels
Beat the set of 16 procedurally generated levels
Beat the first lava challenge
Beat the final challenge
Beat the first inverted challenge
Beat the final inverted challenge