Darx

Darx is a dark-elemental dragon. He is a ghost-type dragon and is Kohei Toki's companion. Able to eat people by feeding on the darkness in their souls. The darker soul, the stronger Darx possession over them.

About
For an unknown amount of time, Darx was under orders to influence the twins Lyn and Sue. Eventually, it is revealed by Sally that the young Lyn and Sue were being controlled by Darx. Darx then revealed himself to Reiji Ozora, claiming that if he were killed, the twins would die along with him. Fortunately, Reiji and Chibi defeated Darx, and Lyn and Sue are released from his control.

After Kohei won the Dragonic Heaven Tournament and gained the Dragonnite, he had Darx attack the three tournament referees who lead him to the Dragonnite in order for him to see it. Darx is last seen in a nightmare Reiji has in which he fails to save Maiko from being kidnapped by Kohei.