Armor Class 18 (natural armor)
Hit Points 337 (27d10 + 189)
Speed 40 ft., fly 40 ft.
Saving Throws DEX +8, CON +14, INT +15, WIS +14
Skills Deception +15, Perception +14, Stealth +8
Damage Resistances cold, fire, lightning
Damage Immunities poison, [object Object]
Condition Immunities charmed, exhaustion, frightened, poisoned
Senses truesight 120 ft., passive Perception 24
Languages all, telepathy 120 ft.
Challenge 23
Legendary Resistance (3/Day). If Fraz-Urb'luu fails a saving throw, he can choose to succeed instead.
Magic Resistance. Fraz-Urb'luu has advantage on saving throws against spells and other magical effects.
Magic Weapons. Fraz-Urb'luu's weapon attacks are magical.
Undetectable. Fraz-Urb'luu can't be targeted by divination magic, perceived through magical scrying sensors, or detected by abilities that sense demons or fiends.
Multiattack. Fraz-Urb'luu makes three attacks: one with his bite and two with his fists.
Bite. Melee Weapon Attack: +16 to hit, reach 10 ft., one target. Hit: 19 (3d6 + 9) piercing damage.
Fist. Melee Weapon Attack: +16 to hit, reach 10 ft., one target. Hit: 22 (3d8 + 9) bludgeoning damage.
Tail. Melee Weapon Attack: +16 to hit, reach 15 ft., one target. Hit: 20 (2d10 + 9) bludgeoning damage. If the target is a Large or smaller creature, it is also grappled (escape DC 24). The grappled target is also restrained. Fraz-Urb'luu can grapple only one creature with his tail at a time.
Phantasmal Killer (Costs 2 Actions). Fraz-Urb'luu casts phantasmal killer, no concentration required.
Mordenkainen's Tome of Foes, p. 146