Duos and Curse of Dragon were used by Seto and Kalim in the battle with Bakura, at Kul Elna. Kalim used the Millennium Scales to fuse the two ka, forming Duos Dragon, whose strength Mahado doubled, using his heka.
Duos Dragon and Diabound's "Dragon Flame" and "Spiral Wave" attacks hit head on. The two blasts pushed against each other, seemingly equal in magnitude, until Diabound's snake appendage used a "Thunder Force" attack, which merged with the "Spiral Wave", causing Diabound's attack to push Duos Dragon's back. Duos Dragon used its sword as a shield against the attack, consequently allowing its hand to be blasted off. This created an opening to hit Diabound with another "Dragon Flame", which was blocked by the ghost of the Kul Elna villagers, whose aura acted as a shield. However the attack began to melt through the shield.
Before Duos Dragon's attack could break through, Bone Snapper shot a blast at Kalim, resulting in his death and Bakura collecting the Millennium Scales as spoils. Without the Millennium Scales to support the fusion, Duos and Curse of Dragon were separated.
The attack from Duos Dragon sufficed to burn a hole in Diabound's shield, which created the opportunity for Mahado to attack and destroy Diabound.
- ↑ Yu-Gi-Oh! Millennium World Duel 39: "Return of the Priests!"
- ↑ 2.0 2.1 2.2 2.3 Yu-Gi-Oh! Millennium World Duel 40: "Together Against the Darkness!"