Here is the full list of all 22 Warlock's Tower achievements.
Reach the game's fourth world
Beat all Warehouse stages
Talk to the Racketboy himself
Play a stage where there's a Slime
Reach the game's third world
Beat all Factory stages
Talk to Jess for the first time
Get the Magic Flag artifact
Reach the game's second world
Beat all Dungeon stages
Talk to Lenda do Herói's Hero
Play a stage where there's a Zombie
Talk to the Evil Warlock for the first time
Reach the game's last world
Talk to Puzzle Depot's Todd Torial
Talk to Möira's Rubick
Talk to Keen's Kim
Play a stage where there's a Fleye
Beat all Library stages
Beat all Chambers stages
Beat all stages of the game
Finish the game