A grease spell covers a solid surface with a layer of slippery grease. Any creature entering the area or caught in it when the spell is cast must make a successful Reflex save or slip, skid, and fall. Those that successfully save can move at half speed across the surface. However, those that remain in the area must each make a new saving throw every round to avoid falling and to be able to move. The DM should adjust saving throws by circumstance. For example, a creature charging down an incline that is suddenly greased has little chance to avoid the effect, but its ability to exit the affected area is almost assured (whether it wants to or not).

The spell can also be used to create a greasy coating on an item—a rope, ladder rungs, or a weapon handle, for instance. Material objects not in use are always affected by this spell, while objects wielded or employed by creatures receive a Reflex saving throw to avoid the effect. If the initial saving throw fails, the creature immediately drops the item. A saving throw must be made each round the creature attempts to pick up or use the greased item.