Mireball

3rd-level conjuration

Casting Time: 1 action
Range: 150 feet (15-foot-radius sphere)
Components: V, S, M (a tiny ball of guano and mud)
Duration: 1 minute
Class: Bard, Druid, Sorcerer, Warlock

A blob of gloopy mud splunks from your pointed finger to a point you choose within range, where it splooges with a wet burp into an explosion of sludge. Each creature in a 15-foot-radius sphere centred on that point must make a Strength saving throw. On a failed save, a target takes 3d10 bludgeoning damage and is knocked prone. On a successful one, it takes half as much damage and is not knocked prone. 

In addition, all surfaces within the area become covered in unpredictably slick and sticky patches of mud for the duration. The first time a creature moves through the muddy area on its turn it must succeed on a Dexterity saving throw against your spell save DC or fall prone. A creature moving through the area at half speed doesn’t need to make the saving throw.

At Higher Levels. When you cast this spell using a spell slot of 4th level or higher, the damage increasesby 1d10 for each slot level above 3rd.

Source: Heliana's Guide to Monster Hunting