Leo of Fairy Tail is supposedly Loki, one of Lucy's Celestial warriors that she summons. Due to some unfortunate circumstances with the shifting weather, Loki, along with the other spirits, have underwent a vast transformation.
Becoming Leo, the leader of the Celestial Spirits and becoming King of the Spirit world. He fights Natsu in one of the dimensions, together with Wendy, Carla and Happy.
Even though Natsu and gang were successful in sealing the spirits. Liberum continues to power the rest of the spirits.
He descends on the team when Natsu and Lucy have chosen to do a job, which unfortunately ends up being a fake mission sent by an unknown person. And Lucy tries to open one of her keys, but yet is unsuccessful.
He is the evil embodiment of Loki. Wears a gold plated armor with a black chest plate.
He's ruthless in what he does. Instead of listening to reason, him and his team wants nothing but the eradication of Natsu's team. To such ends, he would have his own team challenge Natsu to a deadly game.
One spirit for each of Natsu's members.