Armorborn Wyvern

Lesser Legendary Resistance (1/Day). If the wyvern fails a saving throw, it can choose to succeed instead. 

Partially Constructed Nature. The wyvern does not require food or water, and has advantage on saving throws against being poisoned, knocked unconcious, and on exhaustion saving throws.

Multiattack. The wyvern makes two attacks: one with its bite and one with its stinger or Fireball. While flying, it can use its claws in place of one other attack.

Bite. Melee Weapon Attack: +9 to hit, reach 10 ft., one creature. Hit: 16 (2d10 + 5) piercing damage plus 2 (1d4) fire damage.

Claws. Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 16 (2d10 + 5) slashing damage.

Bladed Stinger. Melee Weapon Attack: +9 to hit, reach 10 ft., one creature. Hit: 14 (2d8 + 5) piercing or slashing damage (wyvern's choice). The target must succeed on a DC 16 Strength saving throw or be knocked backward 5 feet from its original location.

Fireball. Ranged Weapon Attack: +7 to hit, range 100/210 ft., one target. Hit: 16 (2d12 + 3) fire damage.

Cloak (Recharge 5-6). The wyvern casts invisibility or see invisibility, targeting itself.

Death Gaze (1/Day). The wyvern makes a Fireball attack on a target within range, which has advantage if the target is vulnerable to fire or magical bludgeoning, piercing, or slashing damage. On a hit, the target takes no damage but must succeed on a DC 18 Constitution saving throw or, if it has 80 hit points or less, drop to 0 hit points immediately.