Fern

Fern (aka Green Finn) is an Adventure Time villain (who used to live on the roof of Jake and Finn's home) and a boss in. Fern appears when Jake, Finn and Marceline are trying to free Princess Bubblegum in the quest Find PB.

It turns out, Fern is leader of the pirates and later flees to the Fire Kingdom, where he was seen by Cinnamon Bun.

Achievements
Players will earn the Grass Cutter achievement, when Fern is defeated.

Fern reappears later in the Fire Kingdom in quest Reach the Core room as the Fire Kingdom core saboteur. He then leaves Finn and the other heroes with a Level 10, 16000 HP strong Automaton named Fire Giant in the core room. It has a cannon, which can use a Blaze Shot attack.

When Finn's party returns to the Ice Kingdom Fern appears together with Gumbald, who has the Enchiridion. While Gumbald battles Finn's party, the Ice King chickens out and runs away and Fern follows him. In the end, Fern is on the loose and frees Gumbald from the Candy Kingdom's dungeon.