Adult Wild Magic Dragon

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

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: +11 to hit, reach 10 ft., one target. Hit: 17 (2d10 + 6) piercing damage.

Claw. Melee Weapon Attack: +11 to hit, reach 5 ft., one target. Hit: 13 (2d6 + 6) slashing damage.

Tail. Melee Weapon Attack: +11 to hit, reach 15 ft., one target. Hit: 15 (2d8 + 6) 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 16 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.

Breath Weapons (Recharge 5–6). The dragon uses one of the following breath weapons.

Weavechaos Breath. The dragon exhales a random element in an 60-foot line that is 5 feet wide. Each creature in that line must make a DC 18 Dexterity saving throw, taking 45 (13d6) Acid, Cold, Fire, Lightining or Thunder damage on a failed save, or half as much damage on a successful one.

Wild Magic Surge The dragon exhales weave tendrils in a 60-foot cone. Each creature in that area must succeed on a DC 18 Constitution saving throw or get filled with Wild Magic for 10 minutes.  Creatures filled with wild magic roll on the wild magic table once per turn every time it takes an action, bonus action or reaction.

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 19 Dexterity saving throw or take 13 (2d6 + 6) bludgeoning damage and be knocked prone. The dragon can then fly up to half its flying speed.

Wild Magic leech. Every time a Wild magic  surge takes affect or the dragon uses a Wild Magic related action, it can recover a number of hit points equal to his constituition bonus plus his proficiency bonus (10)