Arkos

Death Throes. When Arkos dies, it explodes, and each creature within 30 feet of it must make a DC 20 Dexterity saving throw, taking 70 (20d6) fire damage on a failed save, or half as much damage on a successful one. The explosion ignites flammable objects in that area that aren't being worn or carried, and it destroys the Arkos' weapons.

Magic Resistance. The Arkos has advantage on saving throws against spells and other magical effects.

Magic Weapons. The Arkos' weapon attacks are magical.

Multiattack. The Arkos makes two attacks: one with its lightning weapon and one with its fire weapon.

Stormfang. Melee Weapon Attack: +14 to hit, reach 10 ft., one target. Hit: 21 (3d8 + 8) slashing damage plus 13 (3d8) lightning damage. If the Arkos scores a critical hit, it rolls damage dice three times, instead of twice.

Flame Whip. Melee Weapon Attack: +14 to hit, reach 30 ft., up to thee targets. Hit:  10 (3d6) fire damage, this attack can also hit up to two other creature providing they are within 15ft of both the original target and Arkos.

Teleport. The Arkos magically teleports, along with any equipment it is wearing or carrying, up to 120 feet to an unoccupied space it can see.

Igneous Shield. Melee Weapon Attack: +14 to hit, range self., one target. Hit: 14 (2d6+8) fire damage. As a Bonus Action, the target must make a DC 17 Strength saving throw,  taking 14 (2d6+8) fire damage and go prone on a failed save, or half as much damage and don't go prone on a success. +2 AC. 

Flame Rush. As an action, Arkos moves 60ft in one direction. If any creatures are in its path, they must make a  DC 17 Dexterity or Strength saving throw, taking 14 (2d6+8) fire damage and be pushed to the ends of Arkos' path, or half as much damage and not  pushed any distance, additionally if it was a successful Strength saving throw Arkos' movement becomes 0 till the end of his turn. Additionally if a creature is pushed into a terrain feature, such as a wall or a stalagmite, they take  14 (2d6+8) bludgeoning damage.

Lightning Lance. A stroke of lightning forming a line 100 feet long and 5 feet wide blasts out from you in a direction you choose. Each creature in the line must make a Dexterity saving throw. A creature takes 8d6 lightning damage on a failed save, or half as much damage on a successful one.

Change Weaponry. As a Bonus Action, Arkos uses his master of electricity and flame to change his weaponry.

Stormfang. Melee Weapon Attack: +14 to hit, reach 10 ft., one target. Hit: 21 (3d8 + 8) slashing damage plus 13 (3d8) lightning damage. If the Arkos scores a critical hit, it rolls damage dice three times, instead of twice.

Flame Whip. Melee Weapon Attack: +14 to hit, reach 30 ft., up to three targets. Hit: 10 (3d6) fire damage, this attack can also hit up to two other creature providing they are within 15ft of both the original target and Arkos. 

Igneous Shield. Melee Weapon Attack: +14 to hit, range self., one target. Hit: 14 (2d6+8) fire damage. As a Bonus Action, the target must make a DC 17 Strength saving throw,  taking 14 (2d6+8) fire damage and go prone on a failed save, or half as much damage and don't go prone on a success. +2 AC. 

Lightning Lance. A stroke of lightning forming a line 100 feet long and 5 feet wide blasts out from you in a direction you choose. Each creature in the line must make a Dexterity saving throw. A creature takes 8d6 lightning damage on a failed save, or half as much damage on a successful one.