Jade Guardian is a common Creature — Merfolk Shaman card from Ixalan (XLN), collector number 194. Current market price: $0.23 (foil $0.31), TCGplayer market prices via Scryfall.
Hexproof (This creature can't be the target of spells or abilities your opponents control.) When this creature enters, put a +1/+1 counter on target Merfolk you control.