Nebula Subrace

Ability Score Increase. Your Strength score increases by 1.
Astral Attraction. Starting at 3rd level, you can use your action to unleash the potential energy within yourself, causing your body to explode in both size and power. Your transformation lasts for 1 minute or until you end it as a bonus action.
When you first transform, each creature other than you in a 10-foot radius centered on you must succeed on a Dexterity saving throw or take a number of d6s of fire damage from the explosion equal to your proficiency modifier. During the transformation, you shed bright light in a 10-foot radius and dim light for an additional 10 feet. You generate a powerful gravitational field. The area within a 20-foot radius centered on you is considered difficult terrain for all hostile creatures.
Once you use this trait, you can't use it again until you finish a long rest.