Thryx, the Sudden Storm is a rare Legendary Creature — Elemental Giant card from Theros Beyond Death (THB), collector number 309. Current market price: $3.50 (foil $5.32), TCGplayer market prices via Scryfall.
Flash (You may cast this spell any time you could cast an instant.) Flying Spells you cast with mana value 5 or greater cost {1} less to cast and can't be countered.