Sunderflock is a rare Creature — Elemental card from Lorwyn Eclipsed Promos (PECL), collector number 74p. Current market price: $1.65 (foil $3.92), 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.