Instant, XR (1)
Uncommon (U3)
Dwarven Catapult deals X damage divided evenly, rounded down, among all creatures target opponent controls.
"Often greatly outnumbered in battle, Dwarves relied on catapults as one means of damaging a large army."
—Sarpadian Empires, vol. IV
Illus. Jeff A. Menges

10/4/2004: Count the number of creatures on resolution of the spell and divide X by that number at that time. If the number of creatures changes before resolution, the damage done may be different than what you expected.
9/16/2007: For example, if X is 5 and the targeted opponent controls three creatures, Dwarven Catapult deals 1 damage to each of those creatures.
Legal in Vintage (Type 1)
Legal in Legacy (Type 1.5)
Legal in Classic (MTGO)
Legal in Commander