The reason I’m thinking about this is “Ammit Eternal”. Don’t know if that’s the real name, as it was spoiled in Japanese. The translation, via MythicSpoilers, reads like this:
Creature – Zombie Crocodile Demon
Whenever an opponent casts a spell, put a -1/-1 counter on Ammit Eternal.
Whenever Ammit Eternal deals combat damage to a player, remove all -1/-1 counters from it.
That should work well with [scryfall]Hapatra, Vizier of Poisons[/scryfall]
I’m adding the white to play one card, but of course it also comes with sideboard options. That one card being [scryfall]Grind // Dust[/scryfall].
Should the deck try to incorporate [scryfall]Archfiend of Ifnir[/scryfall]? Not sure. It would be hard to do it, because many of the cycling cards just aren’t strong enough for constructed.
[scryfall]Driven // Despair[/scryfall] seems like something [scryfall]Ammit Eternal[/scryfall] would work well with, so I’ll put in one.
4 Hapatra, Vizier of Poisons
4 Channeler Initiate
4 Exemplar of Strength
4 Ammit Eternal
4 Defiant Greatmaw
4 Crocodile of the Crossing
4 Grind // Dust
1 Driven // Despair
2 Nest of Scarabs
2 Hapatra’s Mark
2 Fatal Push
4 Concealed Courtyard
4 Blooming Marsh
4 Hissing Quagmire
4 Scattered Groves
4 Shambling Vent
I’ve tried to setup the manabase in such a way that if you have to play a black source tapped on turn one, you’ll probably be able to play a green source untapped on turn two. That’s why all the Forests.
Now, with the full spoiler, I would definitely replace the Defiant Greatmaws with Obelisk Spiders.