Grease

Source: Player's Handbook

Level 1 Conjuration (Artificer, Sorcerer, Wizard)

Casting Time: Action
Range: 60 feet
Components: V, S, M (a bit of pork rind or butter)
Duration: 1 minute

Nonflammable 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 have the Prone condition. A creature that enters the area or ends its turn there must also succeed on that save or fall Prone.