Large fiend (voidling, demon), unaligned

Armor Class: 16 (natural armor)

Hit Points: 94 9d10+45

Speed: 60 ft

STR

21 +5

DEX

18 +4

CON

21 +5

INT

8 -1

WIS

12 +1

CHA

13 +1

Damage Resistances: Psychic, Acid

Damage Immunities: Poison, Force

Condition Immunities: Charmed, Frightened, Poisoned

Senses: Blindsight 60ft, Darkvision 120 ft, passive Perception 11

Languages: Common, Deep Speech, Infernal, telepathy 60 ft.

Challenge Rating: 9 (4350 xp)

Actions

Multiattack. The armanite makes three attacks: one with its hooves, one with its claws, and one with its serrated tail.   Claws. Melee Weapon Attack: +8 to hit, reach 5 ft, one target. Hit: 10 2d4+5 slashing + 7 2d6 Acid damage.
Hooves. Melee Weapon Attack: +8 to hit, reach 5 ft, one target. Hit: 12 2d6+5 bludgeoning damage.
If the target is a Large or smaller creature, it must succeed on a DC 16 Strength saving throw or be knocked prone.
Serrated Tail. Melee Weapon Attack: +8 to hit, reach 10 ft., one target. Hit: 16 2d10+5 slashing + 5 2d4 Acid damage.   Entopic Lance (Recharge 4-5). The armanite looses a bolt of destructive void in a line that is 60 feet long and 10 feet wide.
Each creature in the line must make a DC 16 Dexterity saving throw. On a fail, they gain 2 levels of exhaustion and take 18 4d8 psychic damage.   Etherealness. The armanite enters the Ethereal Plane from the Material Plane, or vice versa. It is visible on the Material Plane while it is in the Border Ethereal, and vice versa, yet it can't affect or be affected by anything on the other plane.