Arcane Bane

Energy Absorption. Whenever the Arcane Bane is subjected to lightening or Radiant damage, it takes no damage and instead regains a number of hit points equal to the lightening/ Radiant damage dealt.

Immutable Form. The Arcane Bane is immune to any spell or effect that would alter its form.

Planer Anker. The Arcane Bane is immune to any spell or effect that would transport or remove it from its current plane.

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

Magic Resistance. The Arcane Bane has advantage on saving throws against spells and other magical effects.

Reflective Nature. Any time the Arcane Bane is targeted by a Magic Missile spell, a line spell, or a spell that requires a ranged attack roll, roll a d6. On a 1 or 2, the Arcane Bane is unaffected. On the 3 to 4 the spell hits. On a 5 or 6, the Arcane Bane is unaffected, and the effect is reflected back at the caster as though it originated from the Arcane Bane, turning the caster into the target.

Hover. The Arcane Bane hovers a few feet off the ground and is immune to the prone condition and is not slowed by difficult terrain.

Magic Weapons. The Arcane Bane's weapon attacks are magical.

Spellcasting. The Arcane Bane is an 18th-level spellcaster. Its spellcasting ability is Intelligence (spell save DC 20, +12 to hit with spell attacks). It has the following wizard spells prepared and can cast them without semantic or material components:

Cantrips (at will): Light, Minor Illusion, Dancing Lights, fire bolt 

1st level (4 slots): Shield, Magic Missile,  Absorb Elements (at will)

2nd level (3 slots): Blur, Mirror Image, Vortex warp, 

3rd level (3 slots): Counter-spell,  Dispel Magic, Hypnotic Pattern, Lightening Bolt, Major image (at will)

4th level (3 slots): Greater invisibility, Strom Sphere, Resilient Sphere, 

5th level (3 slots): Arcane Hand, Dawn, Mislead, Wall of Light

6th level (1 slot): Chain Lightening, Globe of Invulnerability 

7th level (1 slot): Prismatic Spray, Force-cage, Mirage Arcane (at will)

8th level (1 slot): Sunburst, Anti-magic Field 

9th level (1 slot): Prismatic Wall

Multiattack. The Arcane Bane makes two melee attacks.

Slam. Melee Weapon Attack: +13 to hit, reach 5 ft., one target. Hit: 20 (3d8 + 7) bludgeoning damage.

Spike. Melee Weapon Attack: +13 to hit, reach 10 ft., one target. Hit: 23 (3d10 + 7) slashing damage.

Crystal Swarm (Recharge 5/6).The Arcane Bane creates four (4) small crystal shards in its space. They Float in the air and orbit it for one (1) minute. starting with the Arcane Bane's first turn - and as a bonus action on each of its turns thereafter - it can expend one (1) or two (2) of the shards, sending them streaking toward a point or points it chooses within 120 feet of itself. Then the shard explodes. Each creature within 10 feet of the point where the shard explodes must make a dexterity saving throw DC 20. A creature takes 3d6 lightening and 3d6 pricing damage on a failed save, or half as much damage on a successful save. The shards have a AC of 18 and 25 HP.   

The Arcane Bane 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 Arcane Bane regains spent legendary actions at the start of its turn.

Attack. The Arcane Bane makes one Slam attack or Spike attack.

Teleport (2 actions). The Arcane Bane teleports up to 30 feet to a point it can see.

Arcane Barrage (Costs 3 actions). The Arcane Bane casts one of its prepared spells of 4th level or below.