Thresholder

The Thresholder is a Heartless boss from Kingdom Hearts II.

A giant, two-headed, four-armed Heartless with even bigger arms and hands, it could extend from one side of a large-sized chamber to the other. It is accompanied by Gargoyle Knights, Gargoyle Warriors, and Hook Bats during the battle. In actuality, the Thresholder is simply the Possessor possessing the door to the dungeon in the undercroft of Beast's Castle, which Sora unlocks out of the door twice to defeat. If Sora returns to the undercroft after defeating the Thresholder, Gargoyle Knights and Gargoyle Warriors will appear. It is one of the few bosses that King Mickey will appear in if Sora dies.

Kingdom Hearts II
The doors possessed by Possessor that attacked Sora and his friends.

Possessor was separated from the doors with Release, in which the power of the Keyblade was poured into the keyhole blocked by its arms.

Trivia
The carved doors which later become this Heartless make a cameo appearance in Kingdom Hearts: 358/2 Days.