Fern was nearly killed by Finn and blown into pieces of grass, while chopped off Vader's legs and left him to burn in lava.
Afterward, in the presence of Finn, he feels like embracing his own personal identity leaves him overshadowed and as an inferior copy of Finn, which leads him to attempt a takeover of Finn's life.
A member of , furin is a -like peptidase.
The Journal of Biological Chemistry.
Furin cleaves these sections and activates the proteins.
At the end of the episode the Grassy Wizard was hospitalized and Fern was upset but Jake assured him that he did the right thing.
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.
Fern full title: Fern the Human, formerly known as Grass Finn was the result of and merging into one being.