Benjamin Franklin

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

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

Cantrips (at will): fire bolt, light, mage hand, prestidigitation, shocking grasp

1st level (4 slots): detect magic, identify, mage armor*, magic missile

2nd level (3 slots): detect thoughts, mirror image, misty step

3rd level (3 slots): counterspell, fly, lightning bolt

4th level (3 slots): banishment, fire shield, stoneskin*

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

6th level (1 slot): globe of invulnerability

7th level (1 slot): teleport

8th level (1 slot): mind blank*

9th level (1 slot): time stop

*The archmage casts these spells on itself before combat.

Lighting Rod: Melee Attack  +2 to hit  damage 2D4+6,  reach 5 feet 

Lighting blast: Ranged spell Attack, you swing the rod, and a blast of lighting leaps from the tip up to a range of 30 feet. +6 to hit damage 2D6 plus 10 lightning damage. you have advantage on attack rolls if the target is wearing armor made of metal or covered in water

 As a Bonus Action Benjamin Franklin can lift his pen into the air write the Misty step spell without using a spell spot. Teleporting him to a unoccupied spot within 30 feet.  He does not break concentration when using the spell. 

As the battle begins, Benjamin Franklin is 1d6 rounds away from summoning the Fey Turkey. During that time,  if he receives any damage, he must succeed a  Constitution (Concentration) check as if he were concentrating on a spell. If he fails, the summoning is interrupted.