Balagarn's Iron Horn
From HGWiki
Caster Level(s): Bard 1, Wizard / Sorcerer 2
Innate Level: 2
School: Enchantment
Descriptor(s): Sonic
Component(s): Verbal, Somatic
Range: Personal
Area of Effect / Target: Colossal
Duration: Instant
Additional Counter Spells:
Save: None
Spell Resistance: Yes
Description: The caster creates a deep, resonant vibration that shakes all creatures in the area of effect from their feet if they fail a Strength check (as if the caster had a Strength of 20, +5 per focus (regular, greater, epic, legendary) in Transmutation). Every creature that falls will be knocked down for one round. At caster level 21, the Strength check DC increases from 20 to caster level, and the knockdown duration is doubled to 2 rounds. At caster level 41, the knockdown duration increases to 4 rounds.
Notes: When cast by a Dwarven Warchanter, this spell receives +1 DC per 6 Dwarven Defender levels. The creature's strength is its actual strength score rather than strength modifier, e.g., a creature with 20 strength would get 20 + d20 rather than 5 + d20 to oppose the knockdown.