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 with a longer, more conical shape 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 becomes black and the thorns on its roots are now orange. The apple-like fruits become purple and green, the longer ones become bright yellow, and the Unversed's leaves become an orange-brown color.
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.
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.
 Kingdom Hearts Birth by Sleep
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 Dwarfs 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 battle against the Mad Treant, as it is one of the first boss fights in Ventus's scenario, will test the player's knowledge of Ven's strengths and weaknesses, as well as the game's controls and the mastery of special abilities like Shotlocks. Ventus will have Shotlocks, Command Styles, and D-Links available to him in this battle, so these special powers should be utilized to one's advantage.
The Mad Treant will begin the battle by slowly lumbering around the battlefield. While it is not attacking, rush up to the Unversed boss and attack it with magic or physical combos. Remain cautious, however, as the Mad Treant will proceed to send several bombs raining down in all directions. Chain as many Dodge Rolls together as possible to avoid the attack. The player can then rush up to the boss and attack it, but be careful as it can stomp Ventus if he is too close. Be sure to jump as the Unversed leaps into the air, or else Ventus will be hit by a resulting shockwave. The player should also be careful when it lands as it releases poisonous fruit that leaves purple puddles on impact with the ground. Touching the fruit or the puddles causes poison status. If the Mad Treant plants its root-like legs into the ground, be sure to remain in the air, or else Ventus will be hit with Earth magic as shards of rock fly up at him.
After taking enough damage, the Mad Treant will collapse, stunned. It will also drop several much-needed HP orbs. Pick these prizes up to replenish whatever HP is depleted from Ventus's HP bar and continue the onslaught. As the Mad Treant recollects itself and its HP starts to dwindle, it will repeat past attacks. It gains one deadly new technique however, one that allows it to shoot three large bombs at Ventus. Dodge Roll to avoid them (they can be seen coming based on their shadows, which appear on the ground as they draw near). The Unversed will continue to use slightly more powerful versions of previously used attacks for the majority of the battle after this, so utilize the same strategies as before to avoid them. So long as the player heals when necessary and attacks only when the Mad Treant itself isn't attacking, the battle should be quite simple to win.