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 Hapatra, Vizier of Poisons