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

Pack Tactics. The 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 and the ally isn't incapacitated.

Snow Camouflage. The wolf has advantage on Dexterity (Stealth) checks made to hide in snowy terrain.

Undead Fortitude. If damage reduces the wolf to 0 hit points, it must make a Constitution saving throw with a DC of 5 + the damage taken, unless the damage is radiant or from a critical hit. On a success, the wolf drops to 1 hit point instead.

Multiattack. The wolf makes two attacks, one with its claw and one with it's bite. It can substitute a bite attack for a breath attack if it is available.

Bite. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 11 (2d6 + 4) piercing damage. If the target is a creature, it must succeed on a DC 14 Strength saving throw or be knocked prone.

Claw. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 8 (1d8 + 4) piercing damage.

Rime Breath (Recharge 5–6). The wolf exhales a blast of freezing wind in a 15-foot cone. Each creature in that area must make a DC 14 Dexterity saving throw, taking 22 (4d8 +4) cold damage and 7 (1d8 +2) necrotic damage on a failed save, or half as much damage on a successful one. If the target fails the save by more than 5 they take an additional 5 (1d8) necrotic damage and have their movement speed reduced by half. The target can repeat the saving throw at the end of each of its turns, ending the effect on a success.