The Twilight Thorn is a boss from Kingdom Hearts II.
The Twilight Thorn is a giant Nobody that attacks with lightning-like thorns, and shares properties with other deformed Nobodies: it can stretch and contort its body and possesses remarkable maneuverability.
Only one appears, in Kingdom Hearts II, when Roxas goes to the Station of Awakening. It is interesting to note that when Roxas senses a presence and turns around to see who it is, he sees a person wearing an Organization cloak, just before it turns into the Twilight Thorn. Judging from the figure, it seems to be none other than Roxas himself.
The Twilight Thorn shares many notable similarities with Darkside, a gigantic humanoid Heartless. Both prominently appear in Roxas and Sora's awakenings, respectively, and are the first bosses of the game. They also seem to share close connections with Roxas and Sora (again, respectively): the Twilight Thorn appears as Roxas' former self, while Darkside is born from Sora's shadow.
At the same time, the two creatures share key differences, being a Nobody and a Heartless. Darkside has wild, unkempt hair that covers its face save for two yellow eyes, while the Twilight Thorn has wild blue scarves around its neck, and lacks a face of its own.
Note: The Twilight Thorn is not registerd in Jimminy's yournal until you enter the world that never was. This is strange becouse Sora does'nt meet the Twilight Thorn.