Atlantean Skirmisher is a uncommon Creature — Merfolk Rogue card from Marvel Super Heroes Commander (MSC), collector number 616. Current market price: $0.26 (foil $0.42), TCGplayer market prices via Scryfall.
Whenever this creature attacks, it connives. (Draw a card, then discard a card. If you discarded a nonland card, put a +1/+1 counter on this creature.)