"Astral Overdose"

You open your awareness to the vastness of the cosmos and converge that power into a single point of celestial power. A miniature star forms in your hands, its light growing brighter as you force more of your own life force into its core.

Make a ranged spell attack against one creature within range. On a hit, the target takes 6d8 radiant damage.

If the attack hits, you can choose to suffer up to 3d8 force damage. For every 1d8 force damage you choose to suffer, the attack deals an additional 1d8 radiant damage.

The force damage you suffer from this spell cannot be reduced or prevented. 

When cast with a spell slot of 5th level or higher, the damage increases by 1d8 for each slot level above 4th.