Balrog

Death Throes. When the balor dies, it explodes, and each creature within 30 feet of it must make a DC 25 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. Fire resistance or immunity will prevent this.

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

Drums, Drums in the Deep. Any monster of a challenge rating of 8 or lower will attempt to move away from the balrog in any way when the balrog is within hearing distance of the balrog. Any players within this distance must make a DC 25 wisdom saving throw or become afraid.

Fly. Once a day, if the balrog has taken no damage or been put under any negative condition at any point in the day, the balrog may fly up to 50 feet in the air for no more than 30 minutes at a speed of 100 feet.

Darkvision. The balrog can see in the dark.

Multiattack. The balor makes two attacks: one with its longsword and one with its whip.

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

Whip. Melee Weapon Attack: +18 to hit, reach 30 ft., one target. Hit: 15 (4d6 + 8) slashing damage plus 10 (3d6) fire damage, and the target must succeed on a DC 23 Constitution saving throw or be pulled up to 25 feet toward the balor.

Terror of the Balrog.Every turn during combat, any being not currently afraid and able to see the balrog will become afraid if they fail at a wisdom saving throw with a DC 20. If they fail, they will also have to make a wisdom saving throw every turn with a DC 22. On success, they will no longer be afraid. On failure, they will continue to be afraid and take 2d6+2 neurotic damage{"diceNotation":"2d6+8","rollType":"damage","rollAction":"Terror of the Balrog","rollDamageType":"neurotic"}[/rollable] neurotic damage 

Pulling Whip. If pushed or pulled in any way (including gravity) at least 50ft. from an opponent, it may use the whip attack but if the target fails the DC 23, it will be pulled 50 feet and if failed it will be pulled only 5 feet instead.

Fiery Inferno. Magic Attack: +19 to hit, reach 10 ft., one target. Hit: 21 (10d10 + 15) fire damage. Available once a day.

Power of the Maiar. One per year, the balrog may instead go to half it's maximum health instead of dying.