Murktide Regent is a mythic Creature — Dragon card from Secret Lair Promo (SLP), collector number 17. Current market price: — (foil $2,299.99), 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.