Brimstone Elemental

Magic Resistance. The Brimstone Elemental has advantage on all saving throws against all magical effects.

Multiattack. The Brimstone Elemental makes two Brimstone Fireball attacks, two brimstone dart attacks, or two Brimstone Barrage attacks if inside her rose.

Unarmed Strike. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 6(1d10 + 1) bludgeoning damage plus 14(4d6) fire damage.

Brimstone Dart(Exposed only). Ranged Spell Attack: +11 to hit, range 120 ft., one target. Hit: 16(3d6 + 6) fire damage.

Brimstone Fireball(Exposed only).  The Brimstone Elemental throws a ball of brimstone fire at a creature within 90 ft of her. That creature must make a DC 17 DEX save or take 31(7d8) fire damage on a failed save, and the target starts to burn for 1 minute, and the burn can't be extinguished by any nonmagical means. At the end of each of its turns, the target must succeed a DC 18 CON save, or take 13(3d8) fire damage. If the target drops to 0 hit points from this damage, the target crumbles to ash. On a success, the effect ends on the target.

Brimstone Ray(Recharge 4-6, Exposed only). The Brimstone Elemental fires a ray of brimstone fire from her eye, forcing all the creatures in a 120 ft line that is 5 ft wide make a DC 18 DEX save. On a failed save, a target takes 49(9d10) fire damage, and the target starts to burn for 1 minute, and the burn can't be extinguished by any nonmagical means. At the end of each of its turns, the target must succeed a DC 18 CON save, or take 13(3d8) fire damage. If the target drops to 0 hit points from this damage, the target crumbles to ash. On a success, the effect ends on the target. 

After the Brimstone Elemental makes this attack, all attacks made against her have disadvantage for the rest of the round.

Brimstone Barrage(Rose only). The Brimstone Elemental throws a barrage of brimstone projectiles. All targets in a 3x3 area within 180 ft must make a DC 18 DEX save or take 45(10d8) fire damage on a failure, or half as muc damage on a success. The target(s) also start to burn for 1 minute, and the burn can't be extinguished by nonmagical means. At the end of each target's turn, a target must succeed a DC 18 CON save, or take 13(3d8) fire damage. If a target drops to 0 hit points from this damage, the target crumbles to ash. On a success, the effect ends.

Brimstone Rose(recharge 5-6). The Brimstone Elemental can take cover inside her petals. In this state her speed is reduced to 0 ft, but she takes 1 damage from any damaging source regardless of modifiers. She can choose to stay in this state for as long as she wants, but after coming out, she must recharge this action.