Glacial Aura. At the end of the borthak's turn, slippery ice covers surfaces within 10 feet of the borthak. This ice is difficult terrain. When a creature other than the borthak enters the ice's area for the first time on a turn or starts its turn there, it must succeed on a DC 16 Dexterity saving throw or have the prone condition. The ice disappears at the start of the borthak's next turn.

Webbed Feet. The borthak can move across icy surfaces without needing to make an ability check. Additionally, difficult terrain composed of ice or snow doesn't cost it extra movement.

Multiattack. The borthak makes one Bite attack or uses Noxious Regurgitation if available, and it makes two Stomp attacks.

Bite. Melee Weapon Attack: +12 to hit, reach 5 ft., one target. Hit:16 (2d8 + 7) piercing damage plus 7 (2d6) acid damage.

Stomp. Melee Weapon Attack: +12 to hit, reach 10 ft., one target. Hit:11 (1d8 + 7) bludgeoning damage.

Noxious Regurgitation (Recharge 5–6). The borthak spews acid at a creature it can see within 120 feet of itself. The target must make a DC 21 Constitution saving throw. On a failed save, the creature takes 24 (7d6) acid damage and has the poisoned condition until the start of the borthak's next turn. On a successful save, the creature takes half as much damage only.

Reactive Tail. When a creature within 10 feet of the borthak hits the borthak with an attack roll, the borthak swings its tail in retaliation. The triggering creature and any creature within 5 feet of it must succeed on a DC 16 Dexterity saving throw or take 16 (2d8 + 7) bludgeoning damage.

Move. The borthak moves up to its speed without provoking opportunity attacks.

Bite (Costs 2 Actions). The borthak makes one Bite attack.