Multiattack. The dragon can use its Frightful Presence. It then makes three attacks: one with its bite and two with its claws.

Bite. Melee Weapon Attack: +22 to hit, reach 15 ft., one target. Hit: (4d10 + 10) piercing damage plus (4d10) necrotic damage.

Claw. Melee Weapon Attack: +18 to hit, reach 10 ft., one target. Hit: (4d8 + 12) slashing damage. If the target is a Huge or smaller creature, it is grappled (escape DC 28 STR) and is restrained until this grapple ends. The greatwyrm can four creatures grappled this way at a time.

Tail. Melee Weapon Attack: +18 to hit, reach 20 ft., one target. Hit: (3d10 + 15) bludgeoning damage. If the target is a creature, it must make a DC 28 Strength saving throw or be knocked prone.

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 24 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.

Void Breath (Recharge 5-6). The dragon exhales a necrotic void in a 300-foot cone. Each creature in that area must make a DC 28 Dexterity saving throw, taking 160 (32d10) necrotic damage on a failed save, or half as much damage on a successful one.

Enraging Roar. The dragon roars as an action, every creature within 120ft that can hear the dragon must make DC 24 CHA becoming Reckless on a failure. A creature who is Reckless must attack recklessly (as per the barbarian ability) and has advantage on physical saving throws but disadvantage on mental saving throws, these creatures can repeat the save at the end of each of their turns ending the effect on success. The dragon can use this action a number of times equal to it's proficiency bonus.

Change Shape. The dragon magically polymorphs into a Humanoid or beast that has a Challenge rating no higher than its own, or back into its true form. It reverts to its true form if it dies. Any Equipment it is wearing or carrying is absorbed or borne by the new form (the dragon's choice). In a new form, the Dragon retains its Alignment, Hit Points, Hit Dice, ability to speak, Proficiencies, Legendary Resistance, lair Actions, and Intelligence, Wisdom, and Charisma scores, as well as this action. Its Statistics and capabilities are otherwise replaced by those of the new form, except any Class Features or legendary Actions of that form.

Shadestep. At any point the Greatwyrm can move through the void and reappear in a space of its choosing in a range that it can see.

Voidtouched. Any time that the Greatwyrm is hit by anything, it can turn to the void, allowing every and anything to pass through it as though it isnt there. The Greatwyrm can also use this to pass through other barriers in its path.

The greatwyrm 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 greatwyrm regains spent legendary actions at the start of their turn.

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

Attack. The dragon makes a claw or tail attack.

Wing Attack (Costs 2 Actions). The dragon beats its wings. Each creature within 60 ft. of the dragon must succeed on a DC 26 Dexterity saving throw or take 24 (4d6 + 10) bludgeoning damage and be knocked prone. The dragon can then fly up to half its flying speed.

Ignite Body (Costs 2 Actions). If the dragon is damaged it can take this action. The spaces the dragon has occupied or flown over since the start of it's last turn turns to void as the dragon's body burns, any creature occupying those spaces must make a DC 28 Dexterity saving throw, taking 24d6 necrotic damage on a failure or half as much on a success. A creature with Shadow Dragon Blood on it has to make the save even if it is just adjacent to an effected space, these creature also make the Dexterity saving throw at disadvantage. This void engulfs any nonnative object to the plane that isn't being worn or carried, a object that has Shadow Dragon Blood on it is ignites if is adjacent to an effected space.

Bite. The greatwyrm makes a bite attack.

Shattering Roar (Costs 2 Actions). The greatwyrm unleashes a magical roar. Each creature in a 120-foot-radius sphere centered on the greatwyrm must succeed on a DC 28 Constitution saving throw or take 36 (6d12) thunder damage and be incapacitated until the end of its next turn.

Enraging Roar (Costs 3 Actions). The greatwyrm uses its Enraging Roar action.