Xerath, The Magus Ascendant

Living Arcana. Xerath is composed entirely of crackling, raw, arcana. Any creature that hits Xerath with a weapon attack takes 12 (3d6) lightning damage. Additionally, if Xerath takes force damage, he instead heals for the total damage he would've taken. Finally, Xerath is always under the effects of detect magic.
Mana Surge(20 points/Long Rest). Xerath may recharge his abilities or empower them to grant extra effects. A recharge costs 6 points each time and must be used at the start of his turn instead of rolling for recharge. If Xerath is affected by a 8th or 9th level spell, he regains 4 points.

Spell Turning. Xerath has advantage on saving throws against any spell that would hit only him. If the spell is of 5th level or lower it has no effect on Xerath and, if he succeeds a INT check vs the spell DC, instead targets a creature of his choice within 30ft. of him (using the caster's DC). If Xerath fails this check, he targets a random creature instead (including allies).

Legendary Resistance (3/Day). If Xerath fails a saving throw, he can choose to succeed instead.
Siege Monster. Xerath deals double damage to objects and structures.
Unusual Nature. Xerath doesn't need to breath or eat.

I WILL BE FREE (Mythic Trait; Recharges after a Short or Long Rest). If Xerath would be reduced to 0 hit points, his current hit point total instead resets to 175 hit points, and he recharges Rite of the Arcane. Additionally, if he has no Legendary Resistance charges left, he regains 1 charge.

Multiattack. Xerath makes three Shocking Orb attacks.

Shocking Orb. Ranged Spell Attack: +16 to hit, range 40ft., one target. Hit: 23 (4d6 + 9) lightning damage. Surge (1pt). Target hit must succeed a DC 16 Constitution saving throw or be stunned until the end of their next turn.

Eye of Destruction (Recharge 4-6). Xerath flares arcane energy from above, at a point he can see within 100ft. of him. All creatures (excluding himself) in a 20-foot radius cylinder, centered on that point, must succeed a DC 19 Dexterity saving throw, taking 40 (8d8) force damage. Creatures within 5ft. of the center point have disadvantage on this save. Creatures take half as much damage on a success. Surge(2pts). Creatures cannot benefit from Evasion-like effects or damage resistance to force damage.

Rite of the Arcane (Recharge 6).  Up to 5 creatures or structures of Xerath's choice within 300ft of him must each make a DC 21 Dexterity saving throw, taking 80 (16d8) radiant damage on a failed save, or half as much damage on a successful one. If a target’s saving throw fails by 5 or more, the creature is also stunned until the end of its next turn. Surge(3pts). Xerath targets any number of creatures and structures within 1 mile or him. A structure may be targeted 3 times if no creatures are targeted. If only 3 creatures are targeted, they can be targeted twice each.

Unstable Power. If Xerath hits all three attacks of his multiattack, he may use Eye of Destruction as a bonus action. When used in this way, it deals only 20 (4d8) force damage.

Arcane Rebuke. Xerath counterspell's(4th level) a spell within 80ft. of him. If successful, Xerath deals 2 (1d4) force damage per spell level to the caster.

Xerath 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. Xerath regains spent legendary actions at the start of his turn.

Move. Xerath moves up to his speed.

Immolating Touch. Xerath makes a unarmed strike 18 (3d10) lightning damage.

Arcanopulse (Costs 3 Actions). Xerath releases a blast of thunderous arcana in a line that is 150 feet long and 20 feet wide. Objects in that area take 30 (5d10) thunder damage. Each creature there must succeed on a DC 21 Dexterity saving throw or take 30 (5d10) thunder damage and be flung up to 60 feet in a direction away from the line. If a thrown target collides with an immovable object, such as a wall or floor, the target takes 3 (1d6) bludgeoning damage for every 10 feet it was thrown before impact. If the target would collide with another creature instead, that other creature must succeed on a DC 19 Dexterity saving throw or take the same damage and be knocked prone.

If the Xerath's I WILL BE FREE trait has activated in the last hour, he can use the options below as legendary actions.

Arcanopulse costs 2  legendary actions while I WILL BE FREE is active.

Smite. Xerath makes one Shocking Orb attack.

Imbue (Costs 2 Actions). Lightning temporarily surrounds Xerath, and he gains 40 temporary hit points until the start of his next turn. Until all these temporary hit points are gone, Xerath's Living Arcana trait deals an extra 14 (2d12) lightning damage.