Channeling the essence of destruction, the power of burning hate, and all that will one day ignite and smolder; you summon a 30 ft sphere aura of rainbow coloured flame that emanates from yourself for 1 minute. While in this aura, all resistances and immunities are negated. Additionally, the first time a creature attacks on their turn while within the aura, should their attack hit, it is then treated as a critical for the purposes of damage.   Once the spell ends, a blast of fire emanates from the caster. Each creature in a 20-foot-radius sphere centered on the caster must make a Dexterity saving throw. A target takes 8d6 fire damage on a failed save, or half as much damage on a successful one. The caster is immune to this damage.   In addition to making a concentration check whenever the caster sustains damage, the caster must also make a concentration check at the end of each of their turns to maintain the spell. The DC for maintaining the spell starts at 10 for the first turn, but goes up by 1 for every subsequent turn.