Reef Worm is a rare Creature — Worm card from Masters 25 (A25), collector number 70. Current market price: $0.38 (foil $2.37), TCGplayer market prices via Scryfall.
When this creature dies, create a 3/3 blue Fish creature token with "When this token dies, create a 6/6 blue Whale creature token with 'When this token dies, create a 9/9 blue Kraken creature token.'"