Pack Tactics. The undead wolf has advantage on an attack roll against a creature if at least one of the wolf's allies is within 5 feet of the creature.

Threatening Growl. The undead wolf snarls and growls with its half decayed gums and teeth showing the rotted flesh of a hundred kills. Anything battling this creature has to  make a CON 13 saving throw or else suffer disadvantage for the first 3 rounds of combat with the undead wolf.

Bite. Melee Weapon Attack: +2 to hit, reach 5 ft., one target. Hit: 10 (2d6 + 3) piercing damage. If the target is a creature, it must succeed on a DC 13 Strength saving throw or be knocked prone.

Undead Limbs. When a limb is targetted and gets dismembered, the undead wolf keeps trying to fight with what it has left. Suffers movement penalties depending on limb lost.