When Fern first emerged he looked like a lump of grass with a face but then began to resemble Finn in grass form, even gaining the ability to speak. The Grass Demon instructed the Finn Sword to let it do the talking when they escape.įern emerged in ' Reboot' when the Grass Sword touched the Finn Sword again and began to cover it until Finn's arm detached from his body. Both the Finn Sword and the Grass Demon expressed desire to get out. At an unknown period of time later, the interior of the sword was filled with green cobwebs and the cocoon appeared hardened. The Grass Demon wrapped the sword Finn in goo, forming a cocoon around him. In ' Two Swords,' it is revealed that Fern was created when Finn accidentally broke the Finn Sword with the Grass Sword while fighting Bandit Princess, during ' I Am a Sword.' Some time later a spider-octopus-like Grass Demon interacted with the small Finn inside the sword.