Mimicry.

The dragon can mimic sounds it has heard, including voices. A creature  can tell the sound is an imitation with a successful Wisdom (Insight) check opposed by the dragon’s Charisma (Deception) check.

Overpowering Strength.

When the dragon hits a creature with a melee attack, the target must succeed on a DC 19 Strength saving throw or be knocked prone. 

Warding Tail.

When a creature misses the dragon with an attack, the dragon may use its reaction to make a tail attack against the target.

Multiattack. 

The dragon can use its Frightful Presence. It then makes four attacks; one with its bite, one with its tail, and two with its claws.

Draining Bite. 

Melee Weapon Attack: +11 to hit, reach 5 ft., one creature.

Hit: 31 (4d10 + 9) piercing damage and the dragon gains temporary hit points equal to half the damage dealt. The target must succeed on a DC 21 Constitution saving throw or its hit point maximum is reduced by an amount equal to the damage taken.  This reduction is permanent. The target dies if this effect reduces its hit point maximum to 0. The lost hit points can be restored if the victim drinks or bathes in at least one liter of blood from the dragon who drained them.

Claw.

Melee Weapon Attack: +11 to hit, reach 5 ft., one creature.

Hit: 22 (2d12 + 9) slashing damage.

Tail.

Melee Weapon Attack: +11 to hit, reach 10 ft., one creature.

Hit: 28 (3d12 + 9) piercing damage and the target must succeed on a DC 19 Dexterity saving throw or be restrained by the dragon (escape DC 19).

Frightful Presence. Each creature of the dragon’s choice that is within 120 feet of the dragon and aware of it must succeed on a DC 19 Wisdom saving throw or become frightened for 1 minute. A creature can repeat the saving throw at the end of each of its turns, 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 dragon’s Frightful Presence for the next 24 hours.

Enter the description for how bonus actions work for your monster here.

Warding Tail.

When a creature misses the dragon with an attack, the dragon may use its reaction to make a tail attack against the target.

The dragon 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. The dragon regains spent legendary actions at the start of its turn.

Detect. The dragon makes a Wisdom (Perception) check.

Tail Attack. The dragon makes a tail attack.

Wing Attack (Costs 2 Actions). The dragon beats its wings. Each creature within 10 feet of the dragon must succeed on a DC 22 Dexterity saving throw or take 19 (2d10 + 8) bludgeoning damage and be knocked prone.

Enter the description for how mythic actions work for your monster here.

Mythic Action Name (Costs # Actions). Enter the description for your mythic action.