Ancient Scorpios Wyvern

Dragons Bane. This creature has advantage against any dragon, dragonborn or draconic creature on every roll.

Ancient Knowledge. The Wyvern gains advantage and a +10 to any wisdom saving throw.

Serrated Scales. If The Wyvern is successfully hit by an unarmed strike the attacker is dealt (2d10 slashing) damage. 

Rapid Attacker. This creature may take 5 actions per turn as well as 5 bonus actions per turn.

Legendary Resistance (4/day). The Wyvern may chose to succeed on any failed roll.

Spellcasting. The Scorpios Wyvern is a 20-level spellcaster. Its spellcasting ability is +20 (spell save 20, +18 to hit with spell attacks). The Scorpios Wyvern has following 
1st level (20 slots): Detect Dragon: (detects any dragon, dragonborn or draconic creature in a 600ft radius).

Channel Wind. The Wyvern Takes Flight and launches a massive gust of wind in a 90ft cone in front of itself, any creature caught in the cone must make a dc 20 dexterity or strength check or be pushed backwards 70ft, and takes (3d20 force) damage.

Frightful Presence. Each creature of the Wyvern's choice within 120 feet of it and aware of it must succeed on a DC 17 Wisdom saving throw or become frightened for 2 minutes. A creature can repeat the saving throw at the end of each of its turns, with disadvantage if the Wyvern is within line of sight, ending the effect on itself on a success. If a creature's saving throw is successful or the effect ends for it, the creature is immune to the Wyvern's Frightful Presence for the next 10 hours.

Shattering Roar. A Shattering Roar Is let out, any creature that is able to hear within a 100ft radius from the Wyvern must succeed a dc 20 constitution saving throw, if it fails it becomes stunned and defend for 2 minutes. Any creature within a 80ft radius of the Wyvern must succeed a dc 20 wisdom saving throw, if it fails it becomes frightened for 2 minutes.

Tail Smash. The Wyvern swings its tail in the direction of an enemy, Smashing it down to the ground with lightning speed: +20 to hit, reach 20 ft., 1 target. Hit: 60 (4d20 + 20) [Bludgeoning] damage.

Tail Stab. The Wyvern lashes its tail towards a target attempting to stab it with it's stinger: +20 to hit, reach 20 ft., 1 target. Hit: 60 (4d20 + 20) [Piercing/Poison] damage.

Bite. It bites: +20 to hit, reach 10 ft., 1 target. Hit: 80 (6d20 + 10) [Piercing/poison] damage.

Whenever it is targeted by a spell, action, bonus action or attack it may take 3 legendary actions .

Shattering Roar (Costs 1 Action). A Shattering Roar Is let out, any creature within a 100ft radius from the Wyvern must succeed a dc 20 constitution saving throw, if it fails it becomes stunned and defend for 2 minutes. Any creature within a 80ft radius of the Wyvern must succeed a dc 20 wisdom saving throw, if it fails it becomes frightened for 2 minutes.

Channel Wind (Costs 1 Action). The Wyvern Takes Flight and launches a massive gust of wind in a 60ft cone in front of itself, any creature caught in the cone must make a dc 20 dexterity or strength check or be pushed backwards 70ft.

Defend (costs 1 Action). The Wyvern ensues a defensive posture and gains +15 to its armor class until its next turn (this effect can stack)

Attack (costs 1 Action). The Wyvern does any one of its basic attacks.