Keen Hearing and Smell. The Zarnash has advantage on Wisdom (Perception) checks that rely on hearing or smell.

Pack Tactics. The Zarnash has advantage on an attack roll against a creature if at least one of the Zarnah's allies is within 5 feet of the creature and the ally isn't incapacitated.

Sunlight Vulnerability. If the Zarnash starts its turn in sunlight it must succeed on a DC 27 Constitution saving throw or immediately be reduced to 0 hit points and become petrified. This petrification ignores the Zarnash's normal immunity and is irreversible.

Multiattack. The Zarnash makes one Bite attack and one Claw attack.

Claw. Melee Attack: +5 to hit, reach 5 ft., one target. Hit: 9 (2d8) slashing damage. 

Bite. Melee Attack: +5 to hit, reach 5 ft., one target. Hit: 7 (1d6 + 3) piercing damage, and the target must succeed on a DC 17 Constitution saving throw or receive one petrification counter. Once a creature has a number of petrification counters equal to its CR or character level, it becomes petrified. This petrification can only be undone through a greater restoration spell, wish spell, or similar magic. 

Sentry. When an ally within 120 feet of the Zarnash takes damage from a source the Zarnash can see, the Zarnash can move up to half its movement speed and make one Claw attack against a creature of its choice.