Grease

Level: 1

Casting Time: 1 action

Range: 60 feet

Duration: 1 minute

Slick grease covers the ground in a 10-foot square centered on a point within range and turns it into difficult terrain for the duration.

When the grease appears, each creature standing in its area must succeed on a Dexterity saving throw or fall prone. A creature that enters the area or ends its turn there must also succeed on a Dexterity saving throw or fall prone.

Source: PHB, page 246. Available in the SRD.