Pleiades

Pleiades (Core) is the archbishop of the Church of Marsterria.

Cardinal Pleiades is a faithful subject of the new Pope Kineriusu III, in Verita. And he is the strongest one of 17 Cardinals. He also killed Luna Clear.

Battle Goddess Verita
In Verita, Core (Pleiades) was a boy who believed Celica at first. But after the events in the God cemetery, he began to hate Celica.

Eushully didn't explain why Core is referred to as Pleiades after Verita.

Battle Goddess 2
He was the one that originally requested to free Roka, who was imprisoned due to the events that were laid out at the end of BG1 (Helping the Godslayer). He kept insisting that she is the reincarnation of Luna Clear. Roka denies this, but not due to the fact that she knows about it, but it is because she believes she is Roka, and nobody else. As the story progresses, he was the one that delivered the final blow against the Majin Elteno after being weakened significantly by Celica, who decided he doesn't want to finish her off. As a result, he absorbed her powers and started becoming obsessed in power for his own vision of justice. This is where Roka realizes the fanaticism and decided to end this. They had a duel with believers as spectators in the Grand Church, and he lost. After his defeat, he tells Roka he was a failure and the one that killed Luna Clear, which Roka doesn't feel much as she still doesn't believe she's the reincarnation of Luna Clear.

Celica does not remember anything about Pleiades, so the only reason he's hostile with him is because he's a Godslayer and Pleiades is a Mars Terrier.