Aerial Coordination. While the wyvern mount has a rider, both the mount and rider have advantage on Dexterity saving throws against area effects, such as a red dragon's fiery breath or a fireball spell. Additionally, the wyvern can Dash or Disengage as a bonus action on its turn when the rider uses their action to command it.

Deflective Wings. As a reaction, the wyvern mount can use its wings to shield its rider or an adjacent ally from an attack or spell. The rider or ally gains a +3 bonus to AC until the start of the mount’s next turn. This bonus applies only if the mount is conscious and not restrained.

Soaring Dive (Recharge 5-6). If the wyvern mount dives at least 30 feet straight toward a target and hits it with a melee attack, the target takes an additional 10 (3d6) damage and must succeed on a DC 15 Strength saving throw or be knocked prone. The wyvern mount can immediately pull up to half its flying speed after the attack without provoking opportunity attacks.

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

Bite. Melee Weapon Attack: +7 to hit, reach 10 ft., one target.
Hit: 15 (2d10 + 4) piercing damage.

Claws. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 13 (2d8 + 4) slashing damage.

Stinger. Melee Weapon Attack: +7 to hit, reach 10 ft., one creature.
Hit: 13 (2d8 + 4) piercing damage, and the target must make a DC 15 Constitution saving throw, taking 24 (7d6) poison damage on a failed save, or half as much damage on a successful one.