The archmage has advantage on saving throws against spells and other magical effects.
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 mind blank, stoneskin and mage armor spells on itself before combat.
Melee or Ranged Weapon Attack: +6 to hit, reach 5 ft. or range 20/60 ft., one target. Hit: 4 (1d4 + 2) piercing damage.