Hi, thanks for playing. I think you got it wrong, the lv4 barrack requires 1 troop of each other types which means in order to spawn a DEMON, you have to sacrifice 1 naked dude, 1 archer, 1 knight and some meat, gold in order to spawn them out. And the game is unbeatable if you don't spawn lv4 units btw:v. Hope this help you!