Benthic Biomancer is a rare Creature — Merfolk Wizard Mutant card from Ravnica Allegiance Promos (PRNA), collector number 32p. Current market price: $0.92 (foil $3.33), TCGplayer market prices via Scryfall.
{1}{U}: Adapt 1. (If this creature has no +1/+1 counters on it, put a +1/+1 counter on it.) Whenever one or more +1/+1 counters are put on this creature, draw a card, then discard a card.