A bright spark flashes from your hands and a point you can see within range instantly blossoms with a low roar into a flash of sickening light and devastating force. Select a point within 120 feet, everything in a 10-foot-radius sphere centered on that point must make a Constitution saving throw. A target takes 2d4 radiant damage, 2d4 force damage, and is poisoned for 1 week on a failed save, or half as much damage and is not poisoned on a successful one. A small mushroom cloud then rises from the location. 

Any creature killed by the light is vaporized and only a shadow in the form of that creature’s last pose remains. Non-magical items the creature is wearing or carrying are also destroyed, but any magical items are left undamaged. 

At Higher Levels. When you cast this spell using a spell slot of 2nd level or higher, both damage types increase by 1d4 for each slot level above 1st. When you cast this spell using a spell slot of 3rd level or higher, the radius is of the sphere increases by 5-feet for every two levels above 1st.

(Optional Rule: If this spell is cast using a spell slot of 5th level or higher, the area of effect remains toxic for one year. Any creature that spends at least 6 hours in the area is poisoned for 24 hours. For every 12 hours spent in the area while it is toxic a creature must succeed at a (DC 15) CON save or suffer 1d4 necrotic damage and 1d4 poison damage.)

^Disclaimer: This spell is designed to be the signature spell of a BBE in a campaign for characters level 6-10. This spell could be granted to the party as a reward for defeating that villain. The (optional) residual radiation and vaporizing the targets are intended to “serve as a sort of soft limiter for the player who gains access to it. Since, presumably, they wouldn't want to start irradiating everything or disintegrating their enemies save only for their screaming ashen ghost-prints.” -Yurei1453

(Special acknowledgments go to TrandamorpherDDS, Yurei1453, and Sangheilioz for special contributions to this spell. Additional acknowledgements go to LeviRocks, Mezzurah, and DarkAbyssKeeper.)