Matthew was a character who appeared in "The Mountain." He was the ruler of a mountain named the Mountain of Matthew. He was the distilled body of all the beings who have completed the mountain. He is now one form of the several beings who have merged into him. In the episode, he was met by Finn and Lemongrab after they complete their obstacles.
Matthew was a humanoid with a group of cultist humanoid followers, or a group of humanoids. He has the appearance of a cloud with a hole in his left torso. His top of his head carved a hollow dent inside him.His appearance is similar to Little Dude (character)'s. When he is hit by Lemongrab 3's lemon candies, he disperses into the humanoid cultists who formed him in the past.
Matthew was self-dependent and believed in world domination to restore everything after he has merged enough beings to evolve into his true form. He was also seen to try to merge with Lemongrab in "The Mountain."