Arcane Immortality. If the taisus dies, its body crumbles into glittering dust. It gains a new body after 1d10 days, reviving with all its Hit Points, unless a Wish spell is cast on its remains to prevent the effects of this trait. The new body appears in an unoccupied space within 5 feet of a location designated by the taisus on its creation.
Legendary Resistance (4/Day). If the taisus fails a saving throw, it can choose to succeed instead.
Magic Resistance. The taisus has Advantage on saving throws against spells and other magical effects.
Spellcasting. The taisus casts one of the following spells, requiring no Material components and using Intelligence as the spellcasting ability (spell save DC 21):
At will: Detect Magic, Fireball (level 5 version), Invisibility, Mage Hand
1/day each: Befuddlement, Disintegrate
2/day each: Jallarzi's Storm of Radiance, Plane Shift, Scrying
Protective Magic. The taisus casts Counterspell or Shield in response to the spell's trigger, using the same spellcasting ability as Spellcasting.
Multiattack. The taisus makes two Brain Drain attacks.
Brain Drain. Melee Attack Roll: +13, reach 20 ft. Hit:20 (3d8 + 7) Force damage plus 16 (3d10) Psychic damage, and if the target is a creature with spell slots, it's subjected to the following effect. Constitution Saving Throw: DC 21. Failure: The target's highest-level unexpended spell slot is expended.
Deadly Drain. The taisus makes a Brain Drain attack. The taisus can't take this action again until the start of its next turn.
Teleport. The taisus teleports itself or a willing creature it can see within 10 feet of itself up to 120 feet to an unoccupied space the taisus can see.
Magically Ascended Mage