Efreet's Binding Inferno

You send out lashing tendrils or fire to scorch and bind an enemy you can see within range. A creature you choose within range that is large or smaller must succeed on a Strength saving throw or take 4d8 fire damage and be restrained. A creature restrained takes 4d8 fire damage at the start of its turn, the creature can remake the save at the end of its turn, ending the effect on a success. a creature that passes the initial save takes the fire damage and is not restrained, ending the spell. 

At higher levels. if this spell is cast with a spell slot of 5th or higher, increase the fire damage by 1d8 for each slot level above 4th.