Ardinian, The Storm Caller

Magic Resistance. Ardinian has advantage on saving throws against spells and other magical effects.

Spellcasting. Ardinian is an 18th-level spellcaster. Its spellcasting ability is Intelligence (spell save DC 17, +9 to hit with spell attacks). Ardinian can cast disguise self and invisibility at will and has the following wizard spells prepared:

Cantrips (at will): light, mage hand, shocking grasp, thunderclap

1st level (5 slots): detect magic, identify, mage armor*, thunderwave, absorb elements

2nd level (5 slots): detect thoughts, mirror image, shatter

3rd level (4 slots): fly*, lightning bolt, thunder step, glyph of warding, call lightning

4th level (4 slots): banishment, elemental bane, storm sphere

5th level (3 slots): scrying, wall of force

6th level (3 slots): globe of invulnerability, chain lightning

7th level (2 slots): teleport

8th level (1 slot): mind blank*

9th level (1 slot): time stop,  shapechange

*The archmage casts these spells on itself before combat.

Dagger. Melee or Ranged Weapon Attack: +6 to hit, reach 5 ft. or range 20/60 ft., one target. Hit: 4 (1d4 + 2) piercing damage.

Dagger. Melee or Ranged Weapon Attack: +6 to hit, reach 5 ft. or range 20/60 ft., one target. Hit: 4 (1d4 + 2) piercing damage.

absorb elements

On initiative count 20 the action to the corresponding round takes place.

1: Ardinian summons 2-3 lightning elemental(2 if there are 6 or less players and 3 if there are 6 or more players) minions within 10ft of itself 

2: A thunder cloud forms above, sending bolts of lightning down in 3 20ft radius cylinders on the battlefield. Any creature that starts its turn in the area of effect must make a DC 15 dexterity saving throw or take 4d6 lightning damage on a failed save, or half as much on a successful save. On each turn after this, the mage can spend a bonus action to move an area of effect up to 30ft.

3: Ardinian claps their hands together with a thundering boom, any creature caught in a cone 30ft wide and 120ft long in front of the mage must make a DC17 strength saving throw or be knocked back 30ft, and be deafened until the end of their next turn. If they hit a wall from from being thrown back, they are knocked prone.