Dread.

Any creature, other than a devil, that starts its turn within 10 feet of Bael must succeed on a DC 22 Wisdom saving throw or be frightened of him until the start of its next turn. A creature succeeds on this saving throw automatically if Bael wishes it or if he is incapacitated.

Legendary Resistance (3/Day).

If Bael fails a saving throw, he can choose to succeed instead.

Magic Resistance.

Bael have advantage on saving throws against spells and other magical effects.

Regeneration.

Bael regains 20 hit points at the start of his turn. If he takes cold or radiant damage, this trait doesn't function at the start of his next turn. Bael dies only if he starts his turn with 0 hit points and doesn't regenerate.

Actions

Multiattack.

Bael makes two Hellish Morningstar attacks.

Hellish Morningstar.

Melee Weapon Attack: +13 to hit, reach 20 ft., one target. Hit: 16 (2d8 + 7) force damage plus 9 (2d8) necrotic damage.

Infernal Command.

Each of Bael's allies within 60 feet of him can't be charmed or frightened until the end of his next turn.

Spellcasting.

Bael casts one of the following spells, requiring no material components and using Charisma as the spellcasting ability (spell save DC 21):

At will: alter self (can become Medium), charm person, detect magic, invisibility, major image
3/day each: dispel magic, fly, suggestion, wall of fire
1/day: dominate monster

Teleport.

Bael teleports, along with any equipment he is wearing or carrying, up to 120 feet to an unoccupied space he can see.

Legendary Actions

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

Fiendish Magic. Bael uses Spellcasting or Teleport.
Infernal Command. Bael uses Infernal Command.
Attack (Costs 2 Actions). Bael makes one Hellish Morningstar attack.