Dragonsguard Elite is a rare Creature — Human Druid card from Strixhaven: School of Mages Promos (PSTX), collector number 127p. Current market price: $0.35 (foil $0.27), TCGplayer market prices via Scryfall.
Magecraft — Whenever you cast or copy an instant or sorcery spell, put a +1/+1 counter on this creature. {4}{G}{G}: Double the number of +1/+1 counters on this creature.