Oil

You conjure about a liter of oil.
You may have it cover a surface’s area in a thin sheet, try to cover a creature in it, or have it coat an object or fill a container.

Covering a Surface:
Any creature which enters an oily area must pass a health (reflex) save, or fall prone.
Any creature which stands up from being prone in an oily surface must pass a health (reflex) save, or fall prone again.

A creature which is pushed onto an oily surface keeps going until it reaches the opposite edge of the surface, up to a maximum distance of 35 ft. per round.
Creatures standing on an oily surface have disadvantage on saves and tests of skill to avoid being pushed.
Creatures which are too heavy to push normally may be pushed across an oily surface.

(If the target would be pushed into a mortal hazard which would cause it to instantly or imminently die, such as off a cliff, it gets a health save to avoid being moved into that hazard, but is still moved as far as safely possible.
Being pushed does not provoke attacks of opportunity.)

Covering a Creature:
You may coat a target in oil if it fails a health (reflex) save against this spell.
If it passes this save, the surface below it is affected instead.

Rolls to grab an oiled creature have disadvantage.
An oiled creature has advantage on saves against being restrained.
An oiled creature has disadvantage on saves and tests of skill against being pushed, tripped, and disarmed.
When an oiled creature moves, it must pass a health (reflex) save against this spell or fall prone.
If it stands up from being prone, it must pass another health (reflex) save or fall prone again.
If it passes its save, it does not have to save against the oil covering it to avoid falling prone again this turn.
An oiled creature may spend an action to get a save to remove the oil covering it.

Covering an Object:
You may target an object.
If the object is being held or is on someone’s person, the holder gets a health (reflex) save to avoid this effect.
If it passes its save, the surface below it is affected instead.

Burning Oil:
If the oil is set on fire, it burns, and any creature in contact with the oil takes 1d4 fire damage, and is set on fire, taking 1d4 ongoing fire damage at the start of each of their turns until they are extinguished or the oil burns up. At the end of each round, roll a d10. On a 1, the oil is burned up and the fire ends.
Ongoing damage from burning oil does not stack.
A creature covered in burning oil may spend an action or drop prone and spend its movement to extinguish themselves.

If the oil is burned in a lantern, it lasts a day.