Curse:
The dragon form has a soul of its own and, as such, requires the wearer to make a DC 10 Wisdom saving throw every time the adventurer wishes to change back to their natural form. On a failed save, the DC goes up by 1 point. The wearer takes 4d6 dmg and takes on a level of Corruption. The mannerisms and goals of the adventurer slowly change to those of the dragon. Each failed save adds a level of Corruption, up to six fails. On the sixth fail, the soul of the dragon takes over the body and the adventurer is lost. The dragon will be all that remains and becomes an NPC, with the player's abilities, controlled by the DM. On a successful save, the corruption is removed and the DC is returned to 10.