User blog comment:Jopjopjop/Volume 18 Spoilers/@comment-9141979-20140718064200/@comment-24502975-20140823173619

Valerie used the Holy Grail subconsciously to place a fragment of Balor's consciousness inside Gasper when he was still in his mother's womb. Then Balor showed himself officially when Valerie said it was okay (v16). Technically Gasper would be Crom's "boss" but how they'll get along in the future isn't known thus far (but it'll certainly be interesting).