DuarkX is the fourth evolution of Duark. He evolved by using DarknessX.
- Attribute: DarknessX Darkus
- Power: 1300 Gs (Story)
- Owner: Kurai (Now Blaze)
DuarkX was evolved with a stolen DarknessX card. Since he was filled with rage before, he has become the angriest bakugan alive. It does not take much to make him mad. He is not able to control his anger like he used to. Although when he joined the Guardians, Blitz used to Perfect Core to change him from DuarkX to Light Duark, but kept all the power excluding the rage. Now that Kurai is gone, he is one of Blaze's bakugan. He now lives in Darkus Village.
- Darkus X: Adds 600Gs to DuarkX
- Darkness Strike: Transferrs 500Gs from opp. to DuarkX
- Screaming Dragon: Nullifies opp. ability
- DuarkX Rage: Subtracts 600Gs from opponent, Adds 750Gs to DuarkX
- Torture Agony: Traps opp. in nearly indestructable Dark cage (can be destroyed by Haos attacks)
- DarknessX: Forces any bakugan into DarknessX evolution
- Dark Minds: Allows DuarkX to control any bakugan's mind
- Darkus Boost: Adds 1000 Gs to Duark and reflects the opponent's ability.