Eluge, the Shoreless Sea is a mythic Legendary Creature — Elemental Fish card from Bloomburrow (BLB), collector number 49. Current market price: $4.42 (foil $6.20), TCGplayer market prices via Scryfall.
Eluge's power and toughness are each equal to the number of Islands you control. Whenever Eluge enters or attacks, put a flood counter on target land. It's an Island in addition to its other types for as long as it has a flood counter on it. The first instant or sorcery spell you cast each turn costs {U} (or {1}) less to cast for each land you control with a flood counter on it.