Aetherius Warden

Cosmic Sight. The Aetherius Warden can see 2-miles into the Ethereal and astral planes while on the material plane, and vice versa.

Ethereal Body. The Aetherius Warden can pass through other creatures and objects. It can enter a hostile creatures space and stop there.

Legendary Resistance (3/Day). If the Aetherius Warden fails a saving throw, it can choose to succeed instead.

Magic Resistance. The Aetherius Warden has advantage on saving throws against spells and other magical effects.

Universal collapse(1/day). When the Aetherius Warden is reduced to 0 hitpoints it unleashes its true power regaining 150 hitpoints and gaining the following, these effects last for 12 hours, after this the Aetherius Warden returns to normal losing all the effects except the health.

• Immunity to Bludgeoning, Piercing and slashing from non-magical attacks.
• resistance to all damage types.
• Immunity to magic that would put it to sleep.
• Immunity to being frightened.
• Astral Laser deals 110 (20d10) force damage and ignores resistances and immunity. It's range increases to 300 feet.
• Worm Hole no longer has a recharge.
• Regain all spent legendary resistances.
• Unlocks Astral storm.
• Unlocks light show.

Astral storm. The Aetherius Warden is at the center of a Astral storm 1d6+4 miles in diameter the storm, the Area become heavily obscured and the strong solar winds inflict disadvantage on attack rolls made with non-magical ranged weapon attacks. within 120-feet of the Aetherius Warden at the start of the round roll a d20 to determine what happens that round:

1-5 A miniature black hole appears at an unoccupied point the Aetherius Warden chooses within 120-feet of it. It is a sphere with a 10-foot radius. Creatures within 30-feet of it must make a DC 22 Intelligence saving throw or are dragged into the black hole taking 33 (6d10) Necrotic damage.

6-10 Each creature must make a DC 20 constitution saving throw becoming stunned for 1 minute of a failed save. The creature can repeat the saving throw at the end of each of their turns ending the effect on a success.

11-12 Each creature must make a DC 20 intelligence saving throw taking 22 (4d10) psychic damage on a failed save and half as much on a success.

13-16 Each creature must make a DC 20 Intelligence saving throw or are knocked unconscious for 5 (1d10) minutes; the effect ends if the creature takes damage or if another creature uses an action to shake them awake.

 17-18 A blinding light shines from the Aetherius Warden, Every creature within 120-feet of the Aetherius Warden must make a DC 20 constitution saving throw or become blinded until the end of the Aetherius Warden's next turn and take 11 (2d10) radiant damage.

19-20 nothing happens.

Multiattack. The Aetherius Warden Makes three bite attacks. It can use Cosmic Warp and Worm hole(recharge) at any point.

Bite. Melee Weapon Attack: +19 to hit, reach 10 ft., one target. Hit: 20 (2d10 + 10) piercing damage plus 27 (6d8) Force damage. This is a magic weapon attack. On a critical hit against a target in an astral body (as with the astral projection spell), the Aetherius Warden can cut the silvery cord that tethers the target to its material body, instead of dealing damage.

Astral Laser(Recharge 5-6). The Aetherius Warden chooses a point it can see within 120 feet of it and fire a laser that travels in a 120-foot line that is 10-feet wide. The Aetherius Warden can choose what direction it travels. The Aetherius Warden can stop the laser as long as it has not gone its maximum distance and choose another point it can see within 120 feet of it to continue it, the laser can only hit a creature once. The Laser can hit targets on the Ethereal and Astral Plane from the Material plane and Vice Versa. Each Creature hit by the laser must make a DC 26 Dexterity saving throw, taking 99 (18d10) Radiant damage. 110 (20d10) after Universal collapse.

Cosmic Warp. The Aetherius Warden can enter the Ethereal or Astral planes from the material plane, it can enter the Material and Astral planes from the Ethereal plane and it can enter the Ethereal and Material planes from the Astral plane. The Aetherius Warden cannot affect or be affected by anything on a plane it is not on.

Light show (After Universal Collapse). (Recharge 5-6). The Aetherius Warden creates 16 magical darts. Each dart hits a target of the Aetherius Warden's choice that it can see within 120-feet. Each dart deals 1d4+1 Force damage, the darts all strike simultaneously and can be directed at one or several creatures. 

Worm Hole(Recharge 2-6). The Aetherius Warden targets up to three creatures it can see within 120-feet of it. Each target must succeed a DC 24 Charisma saving throw or be teleported to either the Astral, Ethereal or material planes. They cannot be teleported to a plane it is already on.

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

Bite. The Aetherius Warden makes one bite attack.

Teleport. The Aetherius Warden magically teleports, along with any equipment it is wearing, up to 120-feet to an unoccupied space it can see.

Worm hole (recharge). The Aetherius Warden targets up to three creatures it can see within 120-feet of it. Each target must succeed a DC 24 Charisma saving throw or be teleported to either the Astral, Ethereal or material planes. They cannot be teleported to a plane it is already on.

Cosmic warp (cost 2 actions). The Aetherius Warden can enter the Ethereal or Astral planes from the material plane, it can enter the Material and Astral planes from the Ethereal plane and it can enter the Ethereal and Material planes from the Astral plane. The Aetherius Warden cannot affect or be affected by anything on a plane it is not on.