As an action, slick grease covers the ground in a sphere centered on a point within 18 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 an Acrobatics 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. The grease no longer causes creatures to fall prone. When a creature enters the burning area for the first time on a turn or starts its turn there, the creature must make a Reflex saving throw.
On a failed save, a creature takes 1d6 fire damage and is burning 1.
On a successful save, a creature takes half as much damage and doesn’t start burning.