Merfolk Skydiver is a uncommon Creature — Merfolk Mutant card from The Lost Caverns of Ixalan Commander (LCC), collector number 277. Current market price: $0.31, 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.)