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

Spellcasting. Zereph is an 20th-level spellcaster. Its spellcasting ability is Intelligence (spell save DC 20, +7 to hit with spell attacks). He can cast [Tooltip Not Found] and [Tooltip Not Found],  [Tooltip Not Found] at will and has the following wizard spells prepared:

Cantrips (at will): lightning lure, fire bolt

1st level (5 slots): chaos bolt, chromatic orb, charm person*, absorb elements

2nd level (4 slots): levitate, shatter, shadow blade

3rd level (5 slots): counterspell, lightning bolt, thunder step

4th level (5 slots): blight, storm sphere, [Tooltip Not Found]*

5th level (4 slots): cone of cold, confusion, immolation

6th level (4 slot): Disintegrate, finger of death, Prismatic Spray

7th level (3 slot): teleport

8th level (3 slot): Power word stun,abi-dalzim's horrid wilting,

9th level (2 slot): time stop,blade of disaster,

*The archmage casts these spells on itself before combat.

Shadow Dagger. Melee or Ranged Weapon Attack: +12 to hit, reach 5 ft. or range 20/60 ft., one target. Hit: 33 (3d10 + 4) piercing damage.

Shadow blade,ashardalon's stride

absorb elements,shield