Reckless. Aarbron can choose to have advantage on all melee attacks made until the start of his next turn. All melee attacks made against Aarbron also have advantage against him until the start of his next turn.

Multiattack. Aarbron makes 5 Claw attacks, or 4 Claw attacks and one Bite attack, or one Rend attack and one Bite attack.

Claw. Melee Weapon Attack: +14 to hit, reach 5 ft., 1 target. Hit: 15 (1d12 + 9) piercing damage. 

Bite. Melee Weapon Attack: +14 to hit, reach 5 ft., 1 target. Hit: 14 (1d10 + 9) piercing damage, 16 (4d8) Necrotic Damage. The target hit point maximum is reduced by an amount equal to the necrotic damage taken, and Aarbron regains hit points equat to that amount. The reduction lasts until the target finishes a long rest.

Rend. Melee Weapon Attack: +14 to hit, reach 10 ft., 1 target. Hit: 27 (2d12 + 9) piercing damage. On hit, target makes a DC 20 Constitution saving throw, taking 12 (4d6) necrotic damage on a failed save, or half as much on a successful one. If a creature is reduced to 0 hit points in this way, it dies instantly.

Aarbron 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. Aarbron regains spent legendary actions at the start of its turn.

Shadow (Costs 1 Action). Aarbron creates a shadow copy of himself that lunges up to 30 ft. to a point Aarbron can see within range. The shadow makes one claw attack against the target, then dissolves into shadow.

Rage Chain (Costs 2 Actions). Aarbron can channel his inner beastial rage to make one bite attack against a single target, or target all enemies in a 5 foot radius with claw attacks.

Wrath of Aarbron (Costs 3 Actions). Aarbron stabs his claws into the ground, making spikes emerge around him in a 60 ft. radius. All creatures in range must succeed a DC20 Dexterity saving throw, suffering 25 (5d10) piercing damage on a failed save, or half as much on a successful one.