The Skull Knight is a minor villain in Yu-Gi-Oh! GX. He is a servant to the Supreme King.
The Skull Knight is a green humanoid with a skull for chest armor, and helmet.
At the time the Supreme King was ruling the Duel world some monsters were trying to rebel. One of them was led by the Ancient Brain. When Axel found out that the Ancient Brain was really a traitor and was actually the Skull Knight, both the Skull Knight and Axel duel each other. It seemed that Axel was losing because Skull Knight summoned his most powerful monster; Lycanthrope and was using it effect, however Axel manage to fight back and win the duel.
Skull Knight's Deck is called the Lycanthrope Deck. His strongest card is the Lycanthrope, because of its effect.
- Skull Knight can shapeshift into the Ancient Brain which ironically is one half of the monsters needed to fuse into Skull Knight, the other being Tainted Wisdom.