Astral Dragon

Arcana Astral. Due to the Astral Dragon's connection to the stars it's magic has multiple effects added along with a spells original effect

Spellcasting. The [Astral Dragon] is a 9th-level spellcaster. Its spellcasting ability is [Wisdom] (spell save DC 5, +2 to hit with spell attacks). The [Astral Dragon] has following [Warlock] spells prepared:
Cantrips (at will): [Booming Blade], [Eldritch Blast] 
9th level (5 slots): [Physic Scream], [True Polymorph] [Imprisonment] [Blade of Disaster] [Astral Projection]

Dodge. Has a 50/50 chance to negate 80% of damage.

Scratch. Melee Attack: +5 to hit, reach 15 ft., 3 target. Hit: 5 (5d8 + 8) [damage type] damage. 

Elemental Breath. Ranged Attack: +7 to hit, range 20/50 ft., 7 target. Hit: 7 (5d10 + 8) [fire, poison, thunder, acid, cold, physic, force ] damage.

It can hide with the walls floors and ceilings in the ruins were it resides.

Uncanny Dodge. When an attacker that you can see hits it with an attack, it can use it's reaction to halve the attack’s damage against it.

Reflective Scales. When attacked it can use it's reaction to harden it's scales and negate 60% of incoming damage.

Warrior's eyes. When used will buff it's attack by 15%.

it stares at targets making the scared

Freezing stare (Costs 1 Actions). Damages targets in it's sight giving the frightened, paralyzed, and frozen effect.

It stomps doing high elemental damage.

 Elemental Stomp(Costs 2 Actions). Damages targets within a 90ft radius with random elemental effects.