Ancient Elf

Magic Resistance. The mage has advantage on saving throws against spells and other magical effects. It also has resistance to damage from spells and spell-like effects.

Fortified Mind. The elf is immune to being charmed or frightened, and magic can't put the Ancient Elf to sleep.

High Elven Magic. The mage is a 15th-level spellcaster. Its spellcasting ability is Intelligence (spell save DC 18, +11 to hit with spell attacks). It has the following wizard spells prepared:

• Cantrips (at will): dancing lights, mage hand, message, Legend Lore

• 1st level (4 slots): mage armor, magic missile, shield, absorb elements

• 2nd level (3 slots):  invisibility, Misty Step, Hold Person, Mirror Image

• 3rd level (3 slots): counterspell, dispel magic, fly, Haste, Hypnotic Pattern

• 4th level (3 slots): banishment, polymorph, Dimension Door

• 5th level (2 slots):  wall of force, conjure elemental, Telekinesis

• 6th level (2 slots): flesh to stone, chain lightning, disintegrate

• 7th level (2 slots):  teleport, prismatic spray, reverse gravity, symbol
  
  

Magic Staff. Melee Weapon Attack: +8 to hit, reach 5-10 ft., one target. Hit: 5 (1d6+1) bludgeoning damage plus 10 (2d10) force damage. This item can be looted as a Staff of Power after defeat. If not picked up within 1 minute of defeat, it disappears from existence. 

Elemental Bolt. Ranged Spell Attack: +11 to hit, reach 150 ft., one target. Hit: 15 (3d10) fire, cold, thunder, lightning or force damage (its choice).

Stunning Soliloquy (Recharge 5–6). The high fae unleashes a string of magical words. Each creature of the high fae's choice within 30 feet of itself must succeed on a DC 18 Intelligence saving throw or have the stunned condition for 1 minute. A stunned creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

High Magic Renewal (1/LR). Once per long rest, the Ancient Elf can activate a vast amount of stored magical energy to recharge all of its spell slots. 

Misty Step. Briefly surrounded by silvery mist, you teleport up to 30 feet to an unoccupied space that you can see.

Beguiling Presence. The elf targets a creature it can see within 60 feet of itself. The target must succeed on a DC 17 Wisdom saving throw or have the charmed condition for 1 minute. An affected target can repeat the saving throw at the end of each of its turns and whenever it takes damage, ending the effect on itself on a success. If a target's saving throw is successful or the effect ends for it, the target becomes immune to all elves' Beguiling Presence for the next 24 hours.

Shield. An invisible barrier of magical force appears and protects you. Until the start of your next turn, you have a +5 bonus to AC, including against the triggering attack, and you take no damage from magic missile.