These cards follow the Binsfield classification of demons. As such they are demons with dominion over sins rather than the sins themselves.
Asmodeus is misspelled. Asmodeus gives buffs and debuffs, not merely buffs. Not sure why his ability is called Relief. Perhaps Lust would better be represented by an Anti-Matter type function.
Since Beelzebub, according to Binsfield is associated with Gluttony, it would make sence to make him a devourer (gravity element) rather than trigger deja vu.
Worthy is a poorly explained mechanic. What does it target and how is x derived? If x is derived from the casting cost of Mammon, why not just specify 12 and 24 in the respective text? It might be simpler just to give him a built in Nova/Super Nova ability.
Belphegor seems like an overpriced Purple Nymph. I would focus more on the delay ability and less on the anti-matter for Sloth.
Satan seems the best card of the lot. It would be difficult to get him out and use him, but could be a game-deciding card. His hideously powerful effects are somewhat balanced by his difficulty to use.
I would remove the devourer aspect from Leviathan and give him more of a thieving lobotomy skill, removing attributes and abilities while conferring them to himself. Leave the devour ability to the Lord of Gluttony.
I would have given Lucifer a +1/+1 for each creature with luminescence and the ability to give all your creatures luminescence with the cost of one Darkness. Momentum seems gratuitous and out of Element.
Interesting incorporation of Binsfield's hierarchy into Elements.