Leonin Vanguard is a uncommon Creature — Cat Soldier card from Core Set 2019 (M19), collector number 22. Current market price: $0.30 (foil $0.89), TCGplayer market prices via Scryfall.
At the beginning of combat on your turn, if you control three or more creatures, this creature gets +1/+1 until end of turn and you gain 1 life.