blue hell fire

You summon blue flames from the hells anyone who touches takes 4d12 fire damage or make a dexterity save of 18 or higher.  after level 7 add another 1d12 fire damage per 2 levels of the caster and increase the amount needed to save by 1 per level of the caster after the caster has reached level 9. Once the caster has reached level 10 the caster is immune to this spell as long as they were the one to cast it, at level 13 the casters party is immune to the effects as long as someone in the party has cast it. At level 15 the caster is completely immune to this spell as well as increasing the duration of the spell to 3 days.