Web of flames

You cover the ground is a blazing web in a 30ft cube infront of you.

When the web appears, each creature within its area must make a Dexterity saving throw. On a failed save, a creature takes 4d6 fire damage, or half as much damage on a successful save.

The area is difficult terrain for creatures other than you.

When a creature moves into the area for the first time of it's turn or ends it's turn in the area it must make a Dexterity saving throw. On a failed save, a creature takes 4d6 fire damage, or half as much on a successful save.

At Higher Levels. When you cast this spell using a spell slot of 4th level or higher, the damage increases by 1d6 for each slot level above 3th.