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

Dwarven Resilience. <$title_short_name$> has advantage on saving throws against poison, and has resistance against poison damage.

Spellcasting. Valtagar 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): Otiluke's Resilient Sphere, 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

*Valtagar casts these spells on itself before combat.

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.

Enlarge (Recharges after a Short or Long Rest). For 1 minute, <$short_name$> magically increases in size, along with anything they are wearing or carrying. While enlarged, <$short_name$> is Large, doubles their damage dice on Strength-based weapon attacks (included in the attacks), and makes Strength checks and Strength saving throws with advantage. If <$short_name$> lacks the room to become Large, they attain the maximum size possible in the space available.

Invisibility (Recharges after a Short or Long Rest). <$title_short_name$> magically turns invisible until they attack, cast a spell, or use their Enlarge, or until their concentration is broken, up to 1 hour (as if concentrating on a spell). Any equipment <$short_name$> wears or carries is invisible with them.