This is the second-to-last 'quest' on the Quests list in the 'Doodle God' part of this title (not the 'Doodle Farm' part).
The combinations you want are in the following order:
Fire + Water = Alcohol
Alcohol + Water = Vodka
Fire + Sand = Glass
Human + Metal = Weapon
Human + Weapon = Assassin
Assassin + Water = Pirate
Death + Human = Zombie
Fire + Void = Sun
Human + Tree = Wood
Human + Wheat = Bread
Metal + Water = Quicksilver
Magic + Quicksilver = Philosopher's Stone
Alcohol + Bread = Beer
Alcohol + Grass = Absinthe
Alcohol + Pirate = Rum
Alcohol + Worm = Tequila
Assassin + Chaos = Joker
Death + Religion = Sacrifice
Glass + Magic = Crystal ball
Glass + Sun = Sunglasses
Human + Zombie = Brains
Metal + Philosopher's Stone = Gold
Music + Wood = Guitar
Void + Weapon = Death Star
This will give you the achievement.