Aura of Madness (Recharge 5–6):

The Voidrend Horror radiates an aura in a 30-foot radius. Any creature that starts its turn within the aura must succeed on a DC 18 Wisdom saving throw or be affected by short-term madness (as per the rules for madness) for 1 minute. A creature affected by this madness has its mind overwhelmed by chaotic, incomprehensible visions and is unable to discern friend from foe, randomly attacking the nearest creature on each of its turns. The creature can repeat the saving throw at the end of each of its turns, ending the effect on a success. A creature affected by this is considered charmed

Multiattack:
The Voidrend Horror makes three attacks: two with its Raptorial Claws and one with its Maw.

Raptorial Claws: Melee Weapon Attack: +12  to hit, reach 15 ft., one target. Hit: 24 (4d8 + 6) bludgeoning damage.

If the target is a Large or smaller creature, it is grappled (escape DC 18). Until the grapple ends, the target is restrained, and the Voidrend Horror can't use that Claw on another target.

Maw Bite: Melee Weapon Attack:  +12 to hit, reach 5 ft., one target. Hit: 28 (4d10 + 6) piercing damage.

If a tentacle grapples the target, the target is also pulled into the Voidrend Horror’s gaping maw, causing the creature to be swallowed. A swallowed creature is blinded and restrained and takes 21 (6d6) acid damage at the start of each of the Voidrend Horror's turns. If the Voidrend Horror takes 30 damage or more on a single turn from a creature inside it, the Voidrend Horror must succeed on a DC 20 Constitution saving throw at the end of that turn or regurgitate the swallowed creature, which falls prone in a space within 10 feet of the Voidrend Horror.

Spine Volley (Recharge 5–6): Ranged Weapon Attack: +8 to hit, range 60/120 ft., up to 3 targets. Hit: 16 (3d10 + 6) piercing damage.

The Voidrend Horror fires a volley of razor-sharp spines from its body against up to 3 creatures it can see within range. Creatures hit by this attack must succeed on a DC 17 Constitution saving throw or be paralyzed until the end of the Voidrend Horror's next turn.

Writhing Lunge:
The Voidrend Horror can move up to 20 feet in a straight line toward a creature that it can see and make one Raptorial Claw attack as a bonus action. If this Tentacle attack hits, the target must succeed on a DC 18 Strength saving throw or be knocked prone.

Unstoppable Rampage:
When the Voidrend Horror takes damage, it can move up to half its speed without provoking opportunity attacks.