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

Change Shape. As an action, Zahhak can polymorph into a humanoid or beast form. The effect lasts until Zahhak wishes to return to his true form.

Multiple Heads. The Zahhak has three heads. Whenever Zahhak takes 25 damage or more on a single turn, one of his heads dies. Zahhak dies if all his heads are dead. At the end of each of his turns when he has at least one living head, Zahhak grows one head for each of his heads that died since his last turn, unless he has taken Cold damage since its last turn. Zahhak regains 20 Hit Points when it grows new heads.

Reactive Heads. For each head Zahhak has beyond one, he gets an extra Reaction that can be used only for Opportunity Attacks.

Multiattack. Zahhak makes as many Bite attacks as he has heads or two rend attacks.

Bite. Melee Attack Roll: +8, reach 10 ft. Hit: 10 (1d10 + 5) Piercing damage plus 5 (2d4) Fire damage.

Rend. Melee Attack Roll: +10, reach 10 ft. Hit: (2d6+5) damage plus 3 (1d6) Fire damage.

Fire Breath (Recharge 5-6). Dexterity Saving Throw: DC 17, each creature in a 60-foot long, 5-foot wide Line. Each head can fire its own stream, resulting in a number of lines equal to the number of currently attached heads. Failure: 17 (5d6) Fire damage for each line. Success: Half damage.

Flame Ward (3/Day). Zahhak can utilize the fire spirits circling his body as protection. If a target makes a successful melee attack on Zahhak, he can use his reaction to increase his AC by 3 and inflict 10 (3d6) Fire damage if they miss.

Legendary Action Uses: 3. Immediately after another creature’s turn, Zahhak can expend a use to take one of the following actions. Zahhak regains all expended uses at the start of each of his turns.

Pounce. Zahhak moves half his speed and makes a single Rend attack.

Firey Vitality (Costs 2 Actions). Zahhak can sacrifice his next breath weapon to instead heal 17 hit points.

Tail Swipe (Costs 3 Actions). Zahhak makes a circular sweeping attack with his tail. Dexterity Saving Throw: DC 17, each creature within 15 ft of Zahhak. Failure: 10 (3d6) Bludgeoning damage and the affected are knocked backed 10ft. Success: Half damage.