Dark Thorn is a Kingdom Hearts II Heartless boss. He is a powerful evolution form of the Shadow Stalker Heartless. He is the final boss of the first visit to Beast's Castle.
The Dark Thorn has the ability to turn invisible. Its invisibility is not vey effective though, as a dim outline of the creature can still be seen. Also, when invisible, the Dark Thorn is much faster. The only way to revive its vizibility is to crush a large object on it, the chandelier being the object Sora uses when fighting it.
Dark Thorn's attacks are primarily physical, and it is a relatively weak opponent.