Armor Class 18
Hit Points 152 (16d10 + 64)
Speed 40 ft., fly 60 ft.
Skills Perception +4, Stealth +4
Damage Resistances cold, fire, lightning
Damage Immunities acid, poison
Condition Immunities poisoned
Senses Blindsight 60 ft., passive Perception 14
Languages Abyssal, Infernal; telepathy 60 ft.
Challenge 9
Fiendish Restoration. If the nycaloth dies outside Gehenna, its body dissolves into ichor, and it gains a new body instantly, reviving with all its Hit Points somewhere in Gehenna.
Magic Resistance. The nycaloth has Advantage on saving throws against spells and other magical effects.
Multiattack. The nycaloth makes two Mercurial Axe attacks.
Mercurial Axe. m,r +9, reach 10 ft. or range 30/90 ft. Hit: 18 (2d12 + 5) Slashing damage plus 10 (3d6) Force damage. The axe magically returns to the nycaloth's hand immediately after a ranged attack.
Shadowy Teleport. The nycaloth has the Invisible condition for 1 minute, and it teleports up to 30 feet to an unoccupied space it can see. The condition ends early immediately after it deals damage.
Monster Manual (2024), p. 229