As an action, slick grease covers the ground in a sphere centered on a point within 10 meters and turns it into difficult terrain for the duration.
When the grease appears, each creature standing in its area must succeed on a Reflex saving throw or a Nimbleness check or fall prone. A creature that enters the area or ends its turn there must also make the saving throw or check.
If any fire touches the grease, it ignites and the grease no longer causes creatures to fall prone. A creature that enters the spell’s area for the first time on a turn or starts its turn there must make a Reflex saving throw.
On a failure, it takes 1d6 fire damage and is burning 1.
On a critical failure, it takes twice as much damage and is burning 2.
On a success, it takes half as much damage and is burning half as much.
On a critical success, it takes no damage.