Murktide Regent is a mythic Creature — Dragon card from Modern Horizons 2 Promos (PMH2), collector number 52p. Current market price: $11.91 (foil $16.99), TCGplayer market prices via Scryfall.
Delve (Each card you exile from your graveyard while casting this spell pays for {1}.) Flying This creature enters with a +1/+1 counter on it for each instant and sorcery card exiled with it. Whenever an instant or sorcery card leaves your graveyard, put a +1/+1 counter on this creature.