Sources
CR
Type
Size
Alignment
Movement

Archduke Zariel of Avernus

Large Fiend (devil), Lawful Evil

Armor Class 21 (natural armor)
Hit Points 580 (40d10 + 360)
Speed 50 ft., fly 150 ft.
STR
27
+8
DEX
24
+7
CON
28
+9
INT
26
+8
WIS
27
+8
CHA
30
+10
Saving Throws INT +16, WIS +16, CHA +18
Skills Intimidation +18, Perception +16
Damage Resistances fire, radiant; bludgeoning, piercing, slashing, from nonmagical attacks that aren't silvered
Damage Immunities cold, necrotic, poison
Condition Immunities Charmed, Exhaustion, Frightened, Poisoned
Senses darkvision 120 ft., passive Perception 26
Languages all, telepathy 120 ft.
Challenge 26 (90,000 XP)

Traits

Devil's Sight. Magical darkness doesn't impede Zariel's darkvision.

Magic Weapons. Zariel's weapon attacks are magical. When she hits with any weapon, the weapon deals an extra 36 (8d8) fire damage (included in the weapon attacks below).

Legendary Resistance (3/Day). If Zariel fails a saving throw, she can choose to succeed instead.

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

Regeneration. Zariel regains 20 hit points at the start of her turn. If she takes radiant damage, this trait doesn't function at the start of her next turn. Zariel dies only if she starts her turn with 0 hit points and doesn't regenerate.

Spellcasting

Innate Spellcasting. Zariel's innate spellcasting ability is Charisma (spell save DC 26). She can innately cast the following spells, requiring no material components:

At will: alter self (can become Medium when changing her appearance), detect evil and good, fireball, invisibility (self only), wall of fire

3/day each: blade barrier, dispel evil and good, finger of death

Actions

Multiattack. Zariel attacks twice with her flail and once with Matalotok. She can substitute Horrid Touch for Matalotok.

Flail. Melee Weapon Attack: +16 to hit, reach 10 ft., one target. Hit:17 (2d8 + 8) piercing damage plus 36 (8d8) fire damage.

Matalotok (Warhammer). Melee Weapon Attack: +16 to hit, reach 10 ft., one target. Hit:17 (2d8 + 8) bludgeoning, or 19 (2d10 + 8) bludgeoning damage if used with two hands, plus 36 (8d8) fire damage. In addition, the weapon emits a burst of cold that deals 10 (3d6) cold damage to each creature within 30 feet of it.

Horrid Touch (Recharge 5–6). Zariel touches one creature within 10 feet of her. The target must succeed on a DC 26 Constitution saving throw or take 44 (8d10) necrotic damage and be poisoned for 1 minute. While poisoned in this way, the target is also blinded and deafened. The target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

Teleport. Zariel magically teleports, along with any equipment she is wearing and carrying, up to 120 feet to an unoccupied space she can see.

Legendary Actions

Immolating Gaze (Costs 2 Actions). Zariel turns her magical gaze toward one creature she can see within 120 feet of her and commands it to combust. The target must succeed on a DC 26 Wisdom saving throw or take 22 (4d10) fire damage.

Teleport. Zariel uses her Teleport action.

Lore

Once a mighty angel charged with watching the tides of the Blood War, Zariel succumbed to the corrupting influence of the Nine Hells and fell from grace. Asmodeus admired Zariel's passion for war and offered her rulership of Avernus. She accepted his offer and was transformed by Asmodeus into an archdevil.