Diabolic Soul

Prerequisite Tiefling

Once per day, you can use your action to channel the hellish power that flows through your veins to transform into an avatar of diabolic might. Your teeth elongate into fangs, your horns grow and become more pronounced, your hair turns into roaring hellfire, and your muscles and veins bulge, all of which grants you the following benefits for 10 minutes:

You add your Charisma modifier to attack rolls.
When you hit a creature with a spell attack or weapon attack, you can use a bonus action to set your enemy ablaze with hellfire. The target takes 1d6 fire damage and gets a penalty to its attack rolls equal to your Charisma modifier for the duration of this form. The damage increases by 1d6 at 5th level, 11th, level, and 17th level.
You have advantage on Charisma (Intimidation) checks and creatures have disadvantage against your spells and effects that would cause them to be frightened.