Zoldeo

Zoldeo was a member of the Grimoire Heart and one of the Seven Kin of Purgatory through possession of Capricorn's body.

History
Not much is known about Zoldeo past. Though it assumed he was once a trusted servant to Layla Heartfilia, gaining the Capricorn key after she retired and was expected to hand it over to Lucy when she was ready. But he became twisted and corrupted, swallowed up by the darkness. At one point, he broke a taboo of the Celestial Spirits using his Human Subordination magic and somehow ended up possessing Capricon's body. It's because of this that Capricorn was able to stay in human world for 17 years. It is also presumably during the time not long after, that he was found by Master Hades and joined Grimorie Heart, becoming one of the Seven Kin of Purgatory.

Synopsis
Most of his actions are covered in Capricorn's section, as it is essentially him controlling Capricon's body.

He winds up battling Gray, Lucy, Loki, and Cana on Tenrou Island outclassing all four. Loki sends his teammates away to battle him alone as Zoldeo was using magic that affected humans, but not spirits. Once gone, the two fight with Zoldeo realizing that Lucy is Layla's daughter and vows to kill her. He tries to send his summoned warriors after her, but Leo easily defeats them. Zoldeo then reveals himself as he uses the magic that fused his spirit with Capricorn's body, Human Subordination Magic: Huma-Raise, to take over Leo's body.

He succeeds but is hit from behind by Capricorn who uses a Regulus blast that Leo had transferred into him before Zoldeo swapped bodies. The attack forces Zoldeo from his body and into his original form. He at first rejoices at regaining his body, but as he is now nothing more than a spirit, much to his horror, he starts to dissolve away till he fades to nothing.

Magic and Abilities
Caster Magic User: While possessing Capricorn, Zoldeo was one of the strongest mages to date. He used a Lost Magic called Human Subordination, which allowed him to keep the upper hand in a battle against four of Fairy Tail's mages. Holder Magic User: Zoldeo was also a Celestial Spirit mage, who held a contract with Capricorn the goat.