Growth-Chamber Guardian is a rare Creature — Elf Crab Warrior card from Ravnica Allegiance Promos (PRNA), collector number 128p. Current market price: $0.30 (foil $0.25), TCGplayer market prices via Scryfall.
{2}{G}: Adapt 2. (If this creature has no +1/+1 counters on it, put two +1/+1 counters on it.) Whenever one or more +1/+1 counters are put on this creature, you may search your library for a card named Growth-Chamber Guardian, reveal it, put it into your hand, then shuffle.