Reef Worm is a rare Creature — Worm card from Commander 2021 (C21), collector number 127. Current market price: $0.25, 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.'"