The Prison Keeper is a minor villain in the video game; Kingdom Heart II. It's an Emblem Heartless that attacked Halloween Town.
After Maleficent resurrects Oogie Boogie, she leaves Lock, Shock, and Barrel behind to deal with Sora, his friends and Jack Skellington. She even summons the Heartless known as the Prison Keeper to assist them in battle. Every so often, the Prison Keeper would grab and devour one of the monster children, which grants the Heartless certain powers.
If it would devour Shock, it would gain the ability to spin its arms around, and fire lasers.
If it eats Lock, the Prison Keeper would gain the ability to shoot large fireballs out of its mouth and hands.
And if the Prison Keeper devours Barrel, it would gain the ability to perform a powerful biting attack on just Sora and slash madly. In the end however, Sora, his friends, and Jack Skellington were able to defeat the Heartless and release the children. With their usual disloyalty, Lock, Shock and Barrel immediately revealed Maleficent's plans to Sora.