Avatar of Chaos

Legendary Resistance (2day). If the Avatar of Chaos fails a saving throw, it can choose to succeed instead.

Eldritch Weapons. The Avatar of Chaos' weapon attacks are magical, also when it hits a creature with a weapon attack the creature that was hit takes an additional 8 (2d6) psychic damage

Essence of Eldritch Magic. The Avatar of Chaos can concentrate on up to 2 spells at a time. If it casts another concentration spell while concentrating on 2 other spells, it can choose one spell it was concentrating on and end its effects immediately.

Sire of Insanity.  Whenever a creature within 30ft of the Avatar of Chaos casts a spell of 1st level or higher that creature must roll a d20. If it rolls a 1, roll on the Wild Magic Surge table to create a magical effect. If it normally requires concentration, it doesn’t require concentration in this case; the spell lasts for its full duration.

Multiattack. The Avatar of Chaos makes two Lightning Lance attacks, two Shocking Grasp attacks or one of each.

 Shocking Grasp. Melee Weapon Attack: +8 to hit, reach 10ft., one target. Hit: 10 (2d8 + 4) lightning damage. and if the target is a creature, it is grappled (escape DC 18). Until this grapple ends, the Avatar can't use this tentacle against other targets. The avatar has 2 tentacles, each of which can grapple one target. At the beginning of a grappled creatures turn they take 6 (2d6) lightning damage. 

Lightning Lance. Ranged Weapon Attack: +8 to hit, Range 100/300 ft., one target, Hit: 12 (2d10+4) Each creature within 10ft of the target must make a DC 18 Dexterity saving throw or take 6 (2d6) lightning damage.

Corruption. (Recharge 5-6)  the Avatar of Chaos targets one creature it can see within 60 feet of it. The target must succeed on a DC 18 Constitution saving throw or take 22 (4d6 + 6) necrotic damage and become corrupted for 1 minute. A corrupted creature's flesh twists in alien ways. The creature has disadvantage on attack rolls and its speed is reduced by half. The corrupted creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

Collapse Distance (Recharge 6). The Avatar of Chaos warps space around one creature it can see within 30 feet of it. That creature must make a DC 18 Wisdom saving throw. On a failed save, the target, along with any equipment it is wearing or carrying, is teleported up to 60 feet to an unoccupied space the seer can see, and then each creature within 10 feet of the target's original space takes 39 (4d12) psychic damage. On a successful save, the target takes 19 (2d12) psychic damage and isn't teleported.

Increase Insanity. As a Bonus action the Avatar of Chaos may sacrifice up to 4 spell slots of any level it has access to taking 1d4 force damage per level of spell slot expended. Until the end of its next turn whenever a creature other than it casts a spell the minimum wild magic surge roll increases by the combined level of spells slots sacrificed. (If 4 level one spell slots are sacrificed the minimum wild magic surge number increases to 5 or lower.)