Debilitating Flames

You conjure flaming chains to chain down and weaken your target. The target must succeed on a Dexterity saving throw or have the Restrained condition and reduce its AC by 2 for the duration. At the end of each of its turns, the target takes 2d8 fire damage and repeats the save, ending the spell on itself on a success. When cast by someone attuned to the fire elemental plane in some manner, these chains bypass immunities to conditions and damage, but not resistance.

Using a Higher-Level Spell Slot. You can target one additional creature for each spell slot level above 6.