Cometfall

You conjure a bright, glowing comet, which appears in midair above your enemies, then strikes the ground with tremendous force and a thunderous boom.

(Spell Compendium, p. 50)

Originally posted on D&D tools

Conjuration (Creation)

Level: Druid 6, Cleric 6,
Components: V, S, DF,
Casting Time: 1 standard action
Range: Medium (100 ft. + 10 ft./level)
Effect: 400-pound ball of rock and ice
Area: 5-ft.-radius burst
Duration: Instantaneous
Saving Throw: Reflex half
Spell Resistance: No

You conjure a comet that immediately falls to the ground, dealing 1d6 points of damage per caster level (maximum 15d6) to everything in the area. The force of the comet can also knock creatures over. Creatures who fail their Reflex save are knocked prone. A creature that succeeds on its saving throw takes half damage from the comet and is not
knocked down.

The comet breaks apart on impact, filling the 10-foot-square area with dense rubble (DMG 90).

You must cast this spell in an area with at least 40 feet of vertical space above the point of impact. If you do not have 40 feet of space, the spell fails.