Decimate

You call upon the wrath of all the planes on a group of creatures. Choose any number of creatures within 2000 feet of a point within range. Each creature chosen must succeed on a wisdom save or take 4d6 psychic damage and gain one form of indefinate madness, gaining no madness and taking half damage on a successfull save. Each creature chosen must also make a dex save or take 10d6 fire, 5d6 cold, 5d6 acid, 5d6 poison, 3d6 lightning, 2d6 thunder,  5d6 radient, 5d6 force, and 5d6 necrotic damage, taking half damage on a successful save.  A creature that fails the dex save is also blinded and cannot regain hit points until your concentration on this spell ends. You can repeat these effects on a each creature thst failed either save each round untill you lose your concentration. You can target creatures on a different plane of existance. 

Note- this is designed to be a 12th level spell