Ancient Waabi Dragon

Immortal. The time dragon ages, but it cannot die from old age.

Read the Threads: The time dragon cannot be surprised.

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

Innate Spellcasting (1/Day). The time dragon can innately cast Time stop.

Innate Spellcasting (1/Day). The time dragon can innately cast Imprisonment.

Innate Spellcasting (2/Day). The time dragon can innately cast Bestow Curse.

Innate Spellcasting (each 3/day). The time dragon can innately cast Slow, Blink, and the spell Haste.

The Time dragon can choose which multiattack option to use .

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

Multiattack 2. The Time Dragon can cast two spells.

Multiattack 3. The Time Dragon can cast one spell and attack once with its tail.

Bite. Melee Weapon Attack: +14 to hit, reach 15 ft., one target. Hit: 19 (2d10 + 8) piercing damage plus 9 (2d8) force damage.

Claw. Melee Weapon Attack: +14 to hit, reach 10 ft., one target. Hit: 15 (2d6 + 8) slashing damage.

Tail. Melee Weapon Attack: +14 to hit, reach 20 ft., up to three targets. Hit: 17 (2d8 + 8) bludgeoning damage.

Alien 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 20 Wisdom saving throw or become frightened and have its speed reduced 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 Alien Presence for the next 24 hours.

Disintegrate Breath (Recharge 5–6). The dragon exhales a chaotic blast of green light in a 90-foot cone. Each creature in that area must make a DC 22 Constitution saving throw, taking 72 (16d8) necrotic damage on a failed save, or half as much damage on a successful one. The target is disintegrated if this damage leaves it with 0 hit points

Second chance (3/day). The time dragon can force a creature it can perceive to re roll a d20.

Move. The Time Dragon can move up to half its movement, when it does so any opportunity attacks against have disadvantage. 

The dragon can take 5 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.

Wing Attack (Costs 2 Actions). The dragon beats its wings. Each creature within 15 feet of the dragon must succeed on a DC 22 Dexterity saving throw or take 15 (2d6 + 8) bludgeoning damage and be knocked prone. The dragon can then fly up to half its flying speed.

Cast Spell (Costs 3 Actions). The dragon casts any spell it knows.

The Time Dragons supernatural ability to read all of time means it cannot truly be killed. Upon being reduced to 0hp the Time Dragon turns into a mosaic or green and purple chaotic smoke and then disappears. In d100 days it appears as a dragon egg in a random plane of existence. It holds all of its own memories from its previous life but must regrow from birth again.