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.

Notes

The speed reduction is 50%, and this is applied upon entering the area of effect. (So, for example, having freedom when entering the area of effect negates the speed reduction, even if freedom is lost while in the affected area.) There is no saving throw for this aspect of the spell (but spell resistance does apply).
The chance of falling down occurs every six seconds, independent of whether or not the speed reduction was effective. Spell resistance does not protect from this; staying on one's feet requires passing the saving throw (or immunity to knockdown).
Creatures with woodland stride are immune to this spell, but due to a bug, incorporeal creatures are not.
The speed reduction stacks when multiple grease spells have overlapping areas.