Disaster Radius is a rare Sorcery card from Rise of the Eldrazi (ROE), collector number 141. Current market price: $0.22 (foil $0.56), TCGplayer market prices via Scryfall.
As an additional cost to cast this spell, reveal a creature card from your hand. Disaster Radius deals X damage to each creature your opponents control, where X is the revealed card's mana value.