Nidhogg's appearance is similiar to a large dragon that is many times the size of a regular Duel Avatar. His body has scales that protrude all over. He has two horns attached to the top of his head with another one acting as his nose. His eyes are red with yellow pupils.
Nidhogg is an extremely dangerous and powerful monster who will follow all orders by Sulfur Pot while under the effects of his Enhanced Armament. However, after being freed by it, he instinctively betrayed his master proving that it cares for no one besides itself.
- In Norse mythology, Níðhöggr (Malice Striker, often anglicized Nidhogg) is a dragon who gnaws at a root of the World Tree, Yggdrasil.
- Nidhogg had one of his fangs caught off by Black Lotus.
- When the Mystical Reins were cut off by Lotus, Nidhogg devoured Solfur Pot who put them on him which suggests that the reins inslave Legendary Enemies against their will.