Marshling

Bubbling and oozing from the deepest, dankest swamps, Marshlings live a cyclical life. They start their lives as bogpoles, which when fed a diet of food and lumber can, with the touch of magic, turn into spawns.

If sent out to attack others and conquer land, Spawn can grow into Slime, which can grow into Goo, which can grow into Ooze, which upon death comes back as a Spawn.