Armor Class 15
Hit Points 272 (32d8 + 128)
Speed 30 ft.
Saving Throws CON +11, INT +14, WIS +13
Skills Arcana +14, History +14, Insight +13, Religion +14
Damage Resistances radiant
Damage Immunities poison
Condition Immunities charmed, exhaustion, poisoned
Senses passive Perception 16
Languages Common, Draconic, Elvish
Challenge 21
Ear of the Chosen. Whenever a creature on the same plane of existence as Alustriel speaks Alustriel's name, Alustriel hears her name and the next nine words the speaker utters.
Legendary Resistance (3/Day). If Alustriel fails a saving throw, she can choose to succeed instead.
Special Equipment. Alustriel carries a magic staff known as the Staff of Silverymoon. In the hands of anyone other than Alustriel, the Staff of Silverymoon is a Staff of Power.
Multiattack. Alustriel makes three Staff of Silverymoon attacks or two Reproving Ray attacks.
Staff of Silverymoon. Melee Weapon Attack: +12 to hit, reach 5 ft., one target. Hit: 14 (2d8 + 5) bludgeoning damage plus 38 (7d10) radiant damage.
Reproving Ray. Ranged Spell Attack: +14 to hit, range 120 ft., one target. Hit: 65 (9d12 + 7) force damage, and if the target is a creature, it must make a DC 22 Charisma saving throw. On a failed save, the target has the incapacitated condition until the start of Alustriel's next turn. On a successful save, the target's speed is reduced by 10 feet until the start of Alustriel's next turn.
Argent Blaze (Requires Silver Fire). Alustriel summons a 60-foot cone of silver fire. Each creature in that area must make a DC 22 Dexterity saving throw, taking 77 (14d10) radiant damage on a failed save or half as much damage on a successful one. Additionally, Alustriel or one creature of her choice within 60 feet of her then regains 10 (3d6) hit points.
Silver Fire (2/Day). Brilliant silver fire harmlessly wreathes Alustriel and empowers her. The silver fire lasts for 1 hour or until she has the incapacitated condition or uses another bonus action to quench it. While wreathed in silver fire, Alustriel gains truesight within 30 feet and can use her Argent Blaze action. In addition, Alustriel is unaffected by magic that would ascertain her alignment, creature type, thoughts, or truthfulness.
Shining Counterspell. Alustriel interrupts a creature she can see within 60 feet of herself that is casting a spell. If the spell is 5th level or lower, it fails and has no effect. If the spell is 6th level or higher, Alustriel makes an Intelligence check (DC 10 plus the spell's level). On a successful check, the spell fails and has no effect. Whatever the spell's level, the caster takes 11 (2d10) radiant damage if the spell fails.
VEoR, p. 242