It's Magic

Zak got into playing with magic and learned things from the other side, that he kept solely to himself in fear of losing the one who meant so much to him.
It didn't bother the Crew as much as it should have and they didn't question Zak's odd behavior either, knowing he was private and if it was something life threatening he would tell them.
At a location a ritual goes wrongfully right, not only inviting in a Dark Goddess but also tying together the Soulmates for the rest of eternity.