Whenever I think about Fern, my mind always goes back to the deal Finn made with the Grass Demon. Becoming a sword was already a brutal adjustment for Finn, being trapped in metal, stuck in the dark, but in a weird way, it was still kind of fascinating. Even inside the blade, he could watch the world go by and see all the adventures “outside Finn” was having.

That is, until the window on the Finn Sword shattered and an unexpected visitor slipped in.

Even though the Outside Finn still carried the Grass Sword, it was like the spirit of that weapon got knocked loose during their clash and ended up trapped inside the Finn Sword with sword Finn. And with nothing but time, Finn and the Grass Demon slowly drifted into this strange, reluctant companionship. They’d talk and eventually, the conversation turned toward escape.

By then, Finn wasn’t just tired of the darkness, he was tired of being a sword over all. So the two of them struck a deal, even if Finn didn’t fully understand what he was agreeing to.

The terms of the deal were never spelled out, but the implication feels obvious: in exchange for freeing them both, the Grass Demon would get to “call the shots.” That’s why Fern doesn’t sound like Finn because the Grass Demon expected to take over completely. But the plan didn’t unfold the way either of them imagined. Instead of the demon seizing control, their essences fused and created someone entirely new.

Fern inherited Finn’s memories, but none of his personality. That disconnect tore him apart. He wasn’t Finn, but he wasn’t the Grass Demon either, and the confusion and resentment pushed him to try to erase Finn, both literally and symbolically by taking his place.

How much Finn understood about the deal remains unclear, and whether the Grass Demon intended any of this is just as murky. But despite the chaos of his creation, Fern eventually carved out his own identity. His origins were messy, even tragic, but he still managed to become something more than the sum of the two beings who made him.



Finn’s deal with a demon