So far so good.
i have the feeling that the MC is some kind of a beast, because Lix Tetrax is a demon in Salomon's book, and the greek message sounds like a summon ritual, maybe this can explain why he has such power that even Calypso was surprised, maybe this can explain too why the little girl insist for him to not open the card, because he wasn't ready to deal with his powers, i guess that his powers are sealed, and the card can destroy that seal, but it will take some time for him to be consumed by the darkness inside him. The card is like a fertilizer, it will make his power grow, the problem it that he will not have control. And maybe this can explain why the phone call tell him to find Calypso, she could be the key for him to control his powers, and maybe this can explain his visions, those visions could be peoples who made a pact with him in the past, this could explain why they look inhuman, when they summon you, you give some of your power to those peoples, and your power corrupt them, and you can see them because they could act as a way to remeber you of what you're capable to do if don't control your power.
hmmm......