Clutch of Earth( Complete Mage, p. 40)
You briefly increase the earth's pull on the target creature.
Ability to cast 2nd-level spells,
As long as you have an earth spell of 2nd level or higher available to cast, you can spend a standard action to reduce the speed of any land bound creature within 30 feet of you. The creature's normal land speed, as well as its burrow and climb speeds, decrease by 5 feet per level of the highest level earth spell you have available to cast, to a minimum speed of 5 feet. This effect lasts for 1 round. A successful Fortitude save negates this effect and renders the target immune to the feat's effect for 24 hours. Creatures currently swimming or flying are immune to this effect. As a secondary benefit, you gain a +1 competence bonus to your caster level when casting earth spells.