Archmage's Power Beam

You ignite the power of the Feyworld through your tattoo and unleash a beam that creates a massive explosion at the point of impact. You take 4d6 Radiant damage as you powering up the spell in you'r forearms than shoot the beam. Each creature in a 20-foot-radius Sphere centered on that point makes a Dexterity saving throw, taking 8d12 Force damage and 4d6 Radiant damage on a failed save or half as much damage on a successful one.
every creature in the 60-foot-radius has to has to make constitution saving throw, on failed save the creature is blinded until start of its next turn.
After using the spell you have to roll d8. On nat 1 the power of the Beam was to strong and destroyed your tattoo so you can't use the spell until you get a new one.