Voidlight

For the briefest possible instant, you open a portal into the Void, revealing the hideous lights beyond. Choose one creature you can see to make a Constitution saving throw. The target has advantage on this roll if it can’t see you. On a failed save, the target takes 1d8 radiant damage. If you roll an 8 on any damage die, you can roll an additional d8 and add its damage to the total, rolling again if this die is also an 8, and so on. You can roll a total number of damage dice for this cantrip equal to twice the number of damage dice you initially rolled. This spell's damage increases by 1d8 when you reach 5th level (2d8), 11th level (3d8), and 17th level (4d8).