Balor Lord

Death Throes. When the balor dies, it explodes, and each creature within 30 feet of it must make a DC 21 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 balor’s weapons.

Fire Aura. At the start of each of the balor’s turns, each creature within 5 feet of it takes 10 (3d6) Fire damage, and flammable objects in the aura that aren’t being worn or carried ignite. A creature that touches the balor or hits it with a melee attack while within 5 feet of it takes 10 (3d6) fire damage.

Legendary Resistance (1/Day). If the balor fails a saving throw, it can choose to succeed instead. 

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

Magic Weapons. The balor’s weapon attacks are magical.

Multiattack. The Balor can use its Frightful Presence. It then makes two attacks: one with its longsword and one with its whip. 

Longsword. Melee Weapon Attack: +15 to hit, reach 10 ft., one target. Hit: 21 (3d8 + 8) Slashing damage plus an additional 13 (3d8) Lightning damage. If the Balor scores a critical hit, it rolls damage dice three times, instead of twice.

Whip. Melee Weapon Attack: +15 to hit, reach 30 ft., one target. Hit: 25 (5d6 + 8) Fire damage, and the target must succeed on a DC 23 Strength saving throw or be pulled up to 25 feet toward the balor.

Frightful Presence. Each creature of the balor's choice that is within 120 feet of the balor and aware of it must succeed on a DC 21 Wisdom saving throw or become frightened for 1 minute. A creature cen repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. If a creature's saving throw is successful or the effect ends for it, the creature is immune to the balor's frightful presence for the next 24 hours. 

Meteor Strike (1/Day). While flying, the ballot lord dives at least 40 feet toward a target space on the ground, creating a massive explosion with a 30-foot radius centered on the balor. This sprays rock and fire in all directions and forms a crater the size of the explosion. Each creature within 30 feet of the balor must succeed on a DC 21 Strength saving throw, taking 21 (6d6) Fire damage and 21 (6d6) Bludgeoning damage and is knocked prone on a failed save, or half as much damage and is not knocked prone on a successful one. Additionally, the ground in that area becomes difficult terrain and is engulfed in flames for ten minutes. A creature that starts its turn in the area while it is still in flames takes 10 (3d6) Fire damage. Each 5-foot square portion of the area requires at least 30 minutes to clear by hand. 

Spellcasting. The balor casts one of the following spells, requiring no material components and using Charisma as the spellcasting ability (spell save DC 21, +13 to hit with spell attacks): 

At will: Detect Magic, Fire Bolt (3d10), Polymorph (self only)

3/day each: Dispel Magic, Dominate Person, Telekinesis

1/day each: Dominate Monster, Fire Storm, Power Word: Stun

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

The balor can take three legendary actions, choosing from the options below. Only one legendary action option can be used a time and only at the end of another creature's turn. The balor regains spent legendary actions at the start of its turn. 

Fire Bolt. The balor casts Fire Bolt.

Attack (Costs 2 Actions). The balor makes a melee weapon attack. 

Teleport (Costs 2 Actions). The balor uses Teleport.

Cast a Spell (Costs 3 Actions). The balor uses Spellcasting.