Flammable Body. Whenever Marius is hit by a melee attack, the attacker must succeed on a DC14 Dex save or take 3 (1D4) fire damage

Terrifying Presence. Hostile creature within 10 feet of Marius, must succeed on a DC13 Wisdom save at the start of each of their turns or become frightened until the start of their next turn.

Legendary Resistance (2/Day). If Marius fails a saving throw, it can choose to succeed instead.

Multiattack. Marius makes three melee attacks: two with its infernal axe and one with its tail. It can use Hurl Flame in place of any melee attack.

Infernal Axe. Melee Weapon Attack: +10 to hit, reach 10 ft., one target. Hit: 13 (2d6 + 6) slashing damage.

Tail. Melee Weapon Attack: +10 to hit, reach 10 ft., one target. Hit: 10 (1d8 + 6) piercing damage. If the target is a creature other than an undead or a construct, it must succeed on a DC 17 Constitution saving throw or lose 10 (3d6) hit points at the start of each of its turns due to an infernal wound. Each time Marius hits the wounded target with this attack, the damage dealt by the wound increases by 10 (3d6). Any creature can take an action to stanch the wound with a successful DC 12 Wisdom (Medicine) check. The wound also closes if the target receives magical healing.

Hurl Flame. Ranged Spell Attack: +7 to hit, range 150 ft., one target. Hit: 14 (4d6) fire damage. If the target is a flammable object that isn't being worn or carried, it also catches fire.

Hellfire (Recharge 5-6). Each creature within 10 feet of Marius must make a DC 17 Dexterity saving throw, taking 21 (6d6) fire damage on a failed save, or half as much damage on a successful one.

Marius 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. Marius regains spent legendary actions at the start of his turn.

Remarkable Speed. Marius flies up to 60 feet without provoking opportunity attacks.
Axe Attack. Marius makes an attack with its infernal axe.
Raise The Fallen (Costs 2 Actions). Marius uses dark magic to temporarily raise all dead allied devils of CR3 and lower within 60 feet of Marius. These creatures gain 7 (1D12) temporary hit points for 1 minute.