The Mad Treant is an enemy which can be found exclusively as a boss in the Kingdom Hearts series.
After Ventus meets Snow White and escorts safely through the woods, Snow White explains that she had previously been attacked by a tree. He returns with her to the Dwarfs' cottage; there, Snow White explains she had met a "man with a key-like sword", and was soon attacked by a swarm of Unversed. As Ventus realizes that she means Terra, the Dwarves accuse Terra of summoning the "evil demons". Ventus defends his friend's name to no avail, and when he runs out to the forest to prove Terra's innocence, he encounters the Mad Treant.
The Mad Treant resembles a large, brown tree. Its trunk splits into three large branches, which in turn fork into three more branches, giving it nine branches covered with green leaves. Purple fruit resembling whole apples and blue fruit resembling apple cores hang from its branches. It has four thick roots that it typically keeps out of the ground to use as legs, though it can send them back into the ground. There are three red thorns on each of these roots. The Mad Treant's mouth is a jagged, black opening in the trunk, and it has a vertical split in its trunk between its eyes. Its red eyes are set in a sorrowful expression, and the Unversed insignia is emblazoned on it just under its mouth.
In Kingdom Hearts Birth by Sleep Final Mix, the Mad Treant takes on a darker appearance. Its trunk is black, and the thorns on its roots are yellow. The fruits on its branches are now colored purple and green, and its leaves are a darker green as well.
The Unversed is somewhat similar to the frightening images of trees from Snow White, resulting from the heroine's ordeal while in the forest at night.
The Treant is a common enemy found in many games of the Final Fantasy series, based on the enemy of the same name in the "Dungeons & Dragons" series of games, which is in turn based upon the Ents of J.R.R. Tolkein's Middle-Earth works. "Mad" may reference the brief moments when it surges and goes berserk with darkness. This is similar to how its namesake the Ent (or Treant) behaves while agitated. Once roused from its slow chain of thought, an Ent will basically go "mad", letting its true strength and adamantine qualities show.