Cosmos Dragon

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

Bonding. The dragon can magically bond with one creature it can see, right after spending at least 1 hour observing that creature while within 30 feet of it. The bond lasts until the dragon bonds with a different creature or until the bonded creature dies. This bond has the following effects.

• The dragon and the bonded creature can communicate telepathically if they're on the same plane of existence.
• the dragon can sense direction and distance of the bonded creature if they're on the same plane of existence.
• As an action, the dragon or the bonded creature can sense what the other sees and hears, during which time it loses its own sight and hearing. This effect lasts until the start of its next turn.
• the bonded creature has fire, radiant, and cold resistance
• the bonded creature can speak and read Celestial, Deep Speech, Draconic

invisiblity (5/day). The dragon can as a bonus action becomes invisible. Anything the dragon is wearing or carrying is invisible as long as it is on the dragon's person. The dragon stays invisible until it makes a attack, or casts a spell.

Ethereal Sight. The dragon can see 60 feet into the Ethereal Plane when it is on the Material Plane, and vice versa.

Incorporeal Movement. The dragon can move through other creatures and objects as if they were difficult terrain. It takes 5 (1d10) force damage if it ends its turn inside an object.

Unusual Nature. The dragon doesn't require air, food, drink, or sleep.

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: +17 to hit, reach 15 ft., one target. Hit: 21 (2d10 + 10) piercing damage plus 14 (4d6) fire damage.

Claw. Melee Weapon Attack: +17 to hit, reach 10 ft., one target. Hit: 17 (2d6 + 10) slashing damage.

Tail. Melee Weapon Attack: +17 to hit, reach 20 ft., one target. Hit: 19 (2d8 + 10) bludgeoning damage.

Ethereal Stride. The dragon and up to three creatures within 5 feet of it magically enter the Ethereal Plane from the Material Plane, or vice versa.

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 21 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.

Radiant Breath (Recharge 5–6). The dragon exhales fire in a 100-foot cone. Each creature in that area must make a DC 25 Dexterity saving throw, taking 90 (20d8) radiant damage on a failed save, or half as much damage on a successful one.

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.

Mass Attraction (3 charges). The dragon casuses each creature withing 120 of it, to move 20 feet towards it in a straight line, each creature affected must make a DC 15  dexterity saving throw or fall prone.