Merfolk Skydiver is a uncommon Creature — Merfolk Mutant card from War of the Spark (WAR), collector number 205. Current market price: $0.26 (foil $1.24), TCGplayer market prices via Scryfall.
Flying When this creature enters, put a +1/+1 counter on target creature you control. {3}{G}{U}: Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)