i had a similar idea but was pre-rotation

Humans are Dead

Looks powerful, love the Gift of Immortality - Angelic Accord - Bubbling Cauldron combo!

Agent of the Fates and Keepsake Gorgon could be great additions

Read the Bones is great hand feed for black

Gift of Immortality on Gray Merchant of Asphodel sound like a nice idea, also something to sac it every turn like Bubbling Cauldron or Blood Bairn

maybe drop the Tithe Drinker for some Door of Destinies ?

that card seems to be making tribal decks work now instead of it just being a theme in standard.

i might choose Banisher Priest over Sin Collector , only because you'll be sacing ceatures, and with him, you'll have less of the opponents creatures to deal with, allowing you to play your strategy on your terms.

This deck is poop.

I think with only 22 lands you will be hard pressed to cast Archangel of Thune consistently. I think you could drop her for another human creature.

I'd make the following adjustments:

-2 Archangel of Thune , - 4 Diabolic Tutor , -1 Angelic Accord

• 2 Sin Collector / Lifebane Zombie , +3 Read the Bones , and MAYBE +1 Obzedat, Ghost Council .

If you dropped the cauldrons, you could even add Whip of Erebos for extra "recursion" of your creatures, and you could add the "Ghost Ride the whip" combo with another Obzedat, Ghost Council . If you did, I would suggest adding 1 or 2 more lands however

i've seen similar decks running Bubbling Cauldron for an additional sac outlet. You might look at High Priest of Penance to slow aggro. I don't know if you've seen the hype around the "Boss Ass Witch" deck, but it runs Bogbrew Witch and Festering Newt with alot of these other cards for some pretty gnarly results.