Twilight Thorn is a boss from Kingdom Hearts II.
Twilight Thorns are giant Nobodies that attack with lightning-like thorns. Some believe that they were controlled by Marluxia.
Only appears in Kingdom Hearts II, when Roxas goes to the Station of Awakening. You can't attack it at first because it holds you up in the air with energy. You can defend and counter his first attack with reaction commands. You do the same thing with his other two attacks. If successful in your third counter, it will leave Roxas and Twilight Thorn on the ground. Roxas will get up first and get back the Keyblade. When he gets it back, you can start attacking Twilight Thorn's head. Then it will get up and start attacking and summoning Creepers. Use the reaction commands to avoid it's attacks.
Twilight Thorns have an interesting resemblance to Darkside. They may be related. The game makes a large point about the resemblance; the cinematic before the battle is almost exactly the same as that before Darkside in Kingdom Hearts. Also, while Darkside had unkempt, wild hair that also covered its face, the Twilight Thorn similarly had a wild scarf and no face.