Reflective Carapace. Any time the beast is targeted by a magic missile spell, a line spell, or a spell that requires a ranged attack roll, roll a d6. On a 1 to 5, the beast is unaffected. On a 6, the beast is unaffected, and the effect is reflected back at the caster as though it originated from the beast, turning the caster into the target.

Multiattack. The beast can use its dreadful Presence. It then makes three attacks: one with its ranged attacks and two with its void slash.

Void Slash. Melee Weapon Attack: +19 to hit, reach 20 ft., one target. Hit: 29 (3d12 + 15) slashing damage. 

Doom Blast. RangedWeapon Attack: +19 to hit, range 200 ft/area 30 ft sphere, Hit: 30 (5d10 + 20) force damage.

 Void Breath (Recharge 5–6). The beast exhales void energy in a 100-foot cone. Each creature in that area must make a DC 26 Dexterity saving throw, taking 126 (20d10) force damage on a failed save, or half as much damage on a successful one.

Dreadful Presence. Each creature of the beast’s choice that is within 120 feet of the beast and aware of it must succeed on a DC 23 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 Wall. The beast makes a wall of Invulnerability in front of it self.

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

Void Glaive (Costs 1 Actions).Void Glaive. Melee Weapon Attack: +19 to hit, reach 20 ft., one target. Hit: 29 (5d8 + 15) Force damage 

The beast can take 1 mythic action after 15 turns.

 Doom Plan(Costs 1 Actions) If the beast's hit points drop below 100 it can escape to repair it self.

The beast will not appear for at least 1 month after the action.