Domain expansion-Bahamuts crater

This is the third and most devastating of the four legendary spells one even Tiamat fears herself. Upon using this spell you create a circle ranging from 60ft-300ft from the point you are standing on. all creatures must make a dex saving throw of 15 + your spell modifier. if all creatures make the save they only take half damage and are blinded until their 3rd tun if failed they take the full damage and become permeantly blinded (dose not affect blindsight). Upon casting this spell you create a magical shrine representing Bahamut granting you immunity to radiant damage. Once the spell is cast a magical dragon head appears above right where you are and casts down a powerful magical ray of light within the area of affect causing 12d12 radiant damage. Once the spell ends the shrine disappears and the terrain is completely scorched and a crater is left that is 40ft deep and however wide you made the circle. The spell can be countered.