Magic Resistance. The archmage has Advantage on saving throws against spells and other magical effects.
Marshal Undead. Undead creatures of the archmage's choice in a 60-foot Emanation originating from the archmage have Advantage on attack rolls and saving throws unless the archmage has the Incapacitated condition.
Spellcasting. The archmage casts one of the following spells, using Intelligence as the spellcasting ability (spell save DC 18):
At will: Blight, Detect Magic, Mage Armor (included in AC), Mage Hand, Prestidigitation, Speak with Dead
1/day each: Circle of Death (level 7 version), Create Undead
Protective Magic (3/Day). The archmage casts Counterspell or Shield in response to the spell's trigger, using the same spellcasting ability as Spellcasting.
Multiattack. The archmage makes four Arcane Burst attacks. It can replace one attack with a use of Spellcasting to cast Blight.
Arcane Burst. Melee or Ranged Attack Roll: +10, reach 5 ft. or range 150 ft. Hit:21 (3d10 + 5) Force damage.
Masters of Magic