Sunderflock is a rare Creature — Elemental card from Lorwyn Eclipsed (ECL), collector number 309. Current market price: $1.88 (foil $3.52), TCGplayer market prices via Scryfall.
This spell costs {X} less to cast, where X is the greatest mana value among Elementals you control. Flying When this creature enters, if you cast it, return all non-Elemental creatures to their owners' hands.