Borealis

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.

Bracer of the Winter Wolf. These bracers come in a set of four and are emblazoned with the visage of a winter wolf. 
While wearing all four bracers, your animal companion deals an extra 2d6 cold damage to any target it hits with any unarmed strikes and natural weapons. Additionally, your companion gains resistance to fire damage. 

Boots of the Panther. These boots are made for a four legged animal companion. 
While your animal companion wears these boots, their steps make no sound, regardless of the surface they are moving across. The companion has advantage on Dexterity (Stealth) checks that rely on moving silently.

Blood Pact of the Raven Queen. Roll a d6 and take that damage, Borealis can change all damage it makes to necrotic for one round. 

Multiattack. Can make one attack with a bite, and one attack with a claw.

Bite. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 11 (2d6 + 4) piercing damage. (2d6) cold damage If the target is a creature, it must succeed on a DC 15 Strength saving throw or be knocked prone.

Claw. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 11 (2d6 + 4) slashing damage. (2d6) cold damage.

Cold 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 13 Dexterity saving throw, taking 21 (6d8) cold damage on a failed save, or half as much damage on a successful one.

Arctic Presence. (1/Dusk) Each creatures of the wolf's choice that is within 30 feet makes a DC 15 Constitution save throw or become vulnerable to cold damage for one minute

Shadow Step. When an attack tries to hit, use 1 Reaction to impose disadvantage on the attack and then teleport through shadows to an within 5 feet of an allies shadow within 60 ft.