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

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

Bite. Melee Weapon Attack: +5 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.

Shield Bash. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 13 (3d6 + 4): bludgeoning damage. If the target is a creature, it must succeed on a DC 15 Strength saving throw or be knocked prone.

Nightmare Howl. The Abyssal Dire Wolf howls and resurrects three wolves around it to attack. They disappear after three turns. They also attack on the Abyssal Dire Wolf's initiative. Recharges after a short/long rest. Read/paraphrase this when the wolf uses this action:

The wolf howls a dreadful howl and the ground starts shaking. Around it three wolves rise from the ground, fur hanging off them in shreds, hearts still beating under their visible rib cage. They growl and leap to attack.