Bursting Finale

You pour all your magic reserves into one final burst of pure, divine, radiance. You create a50ft pillar that instantly destroys all non-legendary undead inside it, and all other creatures take 11d10 radiant damage. After casting this spell, you must succeed on a DC25 constitution check or fall to zero hit points and be unable to be stabilized by any means(non magical or magical) until you succeed on 3 death saving throws.