Archsorcerer

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

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

Cantrips (at will): fire bolt, light, mage hand, prestidigitation, acid splash

1st level (4 slots): detect magic, color spray, mage armor, magic missile

2nd level (3 slots): hold person, mirror image, misty step

3rd level (3 slots): counterspell, fly, fireball

4th level (3 slots): greater invisibility, ice storm, polymorph

5th level (3 slots): cone of cold, dominate person, wall of stone

6th level (1 slot): disintegrate

7th level (1 slot): plane shift

8th level (1 slot): incendiary cloud

9th level (1 slot): gate

*The archmage casts mage armor on itself before combat. 

Metamagic (5/Day): The archsorcerer can twist spells to suit their needs. When casting a spell, they can apply one of the following effects:
Quickened Spell: if the spell has a casting time of 1 action, the archsorcerer changes the casting time to 1 bonus action for that casting.
Subtle Spell: the sorcerer changes the spell to cast it without any somatic or verbal components.
Heightened Spell: if the spell forces a creature to make a saving throw to resist its effects, the archsorcerer gives one target if the spell disadvantage on its first saving throw made against the spell.

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.