Domain of destruction

This spell lets the caster instantly create a 10 FT circle of pure absolute destruction around any being within their line of sight. While the spell is active the being inside the circle takes 8d8 worth of damage per round. This spell last for three rounds or until line of sight is broken. This spell due to being very taxing on both the mind and body of the caster leaves them unable to attack for their next two turns. This spell can only be safely cast once a day if attempting to cast this spell a second time in one day the caster needs to roll a constitution saving throw of 18 or higher. If the saving throw fails the caster then takes 4d6 of damage and is put in a coma like state for 2 days. Every 6 character levels adds 1d6 of damage. At character levels 7 and under you have 1d6 chance (3 and under= pass, 4 and higher= fail) of taking 3d4 of damage while casting the spell.