Grease

Spell level: bard 1; druid 1; ranger 1; sorcerer/wizard 1
Innate level: 1
School: conjuration
Components: verbal, somatic
Range: long (40 meters)
Area of effect: medium (3.33 meter radius)
Duration: 2 rounds + 1 / 3 levels
Save: reflex
Spell resistance: yes
Additional counterspells: freedom of movement

Description: A churning field of oil and grease fills the target area, causing all within to either fall down or move at a reduced speed.

[edit] Notes

The speed reduction is applied when a creature enters the area of effect. The chance for being knocked down occurs every 6 seconds while a creature is in the area of effect.
Spell resistance applies to the reduced speed but not to the knockdown.
Saving throws apply to the knockdown but not to the reduced speed.
A creature with the freedom effect is immune to the speed reduction, but not to being knocked down.
The effects of this spell accumulate when cast multiple times over the same area. For each grease in effect, a reflex save is made to avoid the knockdown effect, and a speed decrease of 50% is applied (to a minimum of 10% following the rules of movement rate).