Chains of fire

chains fill a 15-foot square on ground that you can see within range. For the duration, these chains turn the ground in the area into difficult terrain.

When a creature enters the affected area for the first time on a turn or starts its turn there, the creature must succeed on a Dexterity saving throw or take 3d6 burning damage

A creature that starts its turn in the area and takes 3d6 burning damage