Balrog

Legendary Resistance (3/Day). If the Balrog fails a saving throw, it can choose to succeed instead.

Death Throes. When the Balrog 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 Balrog's weapons.

Fire Aura. At the start of each of the Balrog's turns, each creature within 20 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 Balrog or hits it with a melee attack while within 5 feet of it takes 10 (3d6) fire damage.

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

Magic Weapons. The Balrog's weapon attacks are magical.

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

Longsword. Melee Weapon Attack: +17 to hit, reach 10 ft., one target. Hit: 21 (2d12 + 14) slashing damage plus 13 (3d8) fire damage. If the balrog scores a critical hit, it rolls damage dice three times, instead of twice.

Whip. Melee Weapon Attack: +14 to hit, reach 30 ft., one target. Hit: 15 (2d10 + 14) slashing damage plus 10 (3d6) fire damage, and the target must succeed on a DC 20 Strength saving throw or be pulled up to 25 feet toward the balrog.

Tail. Melee Weapon Attack: +17 to hit, reach 20 ft., one target. Hit: 20 (2d10 + 10) bludgeoning damage.

Evil Presence. Each creature of the balrog's choice that is within 120 feet of the balrog and aware of it must succeed on a DC 21 Wisdom saving throw or become evil for 1 minute. A creature can 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 balrog's Evil Presence for the next 24 hours.

Fire and Lava Breath (Recharge 5–6). The balrog exhales fire and lava in a 90-foot cone. Each creature in that area must make a DC 24 Dexterity saving throw, taking 91 (26d6) fire damage on a failed save, or half as much damage on a successful one.

The Balrog can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The balrog regains spent legendary actions at the start of its turn.

Move. The balrog moves up to half its speed.

Tail Attack. The balrog makes a tail attack.

Wing Attack (Costs 2 Actions). The Balrog beats its wings. Each creature within 15 feet of the balrog must succeed on a DC 25 Dexterity saving throw or take 17 (2d6 + 10) bludgeoning damage and be knocked prone. The balrog can then fly up to half its flying speed.