Ethos/Deck means the influencing potential of your OC.

[b]God[/b] means you're beloved by the Gods, this is usually for God Slayers, you use Ether.

[b]Angel[/b] or Devil/Demon means you're beloved by Angels and likewise you're default highly bound to great Mana, Spiria and Curse potency, making your Deck as pure as possible, hence Ether.

[b]Dragon[/b] means potency to use Dragon Slayer Magic, you may have the Dragon gene but not the ability to use DSM, hence Mana.

[b]Celestial[/b] means you have high potency for Spiritual Arts and Deck is Spiria, you're also beloved by Yokai and the Celestials.

[b]Man[/b] means you're normal, hence Mana.

Take Note: Yokai ain't Demons in Fairy Tail but conceptual spirits.