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

Magic Resistance. The Chaos Dragon has advantage on saving throws against spells and other magical effects. 

Chaos Damage Resistance. The Chaos Dragon's resistance is determined by rolling d%: 01–20 acid, 21–40 cold, 41–60 electricity, 61–80 fire, 81–100 thunder. This trate is rolled each long rest

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: +12 to hit, reach 10 ft., one target. Hit: 18 (2d10 + 7) piercing damage plus 5 (1d10) lightning damage.

Claw. Melee Weapon Attack: +12 to hit, reach 5 ft., one target. Hit: 14 (2d6 + 7) slashing damage.

Tail. Melee Weapon Attack: +12 to hit, reach 15 ft., one target. Hit: 16 (2d8 + 7) bludgeoning damage.

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 17 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.

Confusion Breath (Recharge 5–6). The dragon exhales poisonous gas in a 60-foot cone. Each creature in that area must make a DC 18 Wisdom saving throw. On a success, nothing happens. On a failure, each Target is under the effect of the Confussion Spell

Chaos Breath (Recharge 5-6). The dragon exhales a 30-­foot line of energy that is 5 feet wide. Each creature in that line must make a DC 13 Dexterity saving throw, taking 22 (4d10) random damage on a failed save, or half as much damage on a successful one. The energy type of its breath weapon is determined randomly each time it uses the breath weapon by rolling d%: 01–20 acid, 21–40 cold, 41–60 electricity, 61–80 fire, 81–100 thunder. Even the dragon itself doesn’t know which type of energy it will emit before it actually breathes

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.

Wing Attack (Costs 2 Actions). The dragon beats its wings. Each creature within 10 feet of the dragon must succeed on a DC 20 Dexterity saving throw or take 14 (2d6 + 7) bludgeoning damage and be knocked prone. The dragon can then fly up to half its flying speed.