Amaruq (giant wolf mount of Wulfgarin des'Mond)

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

Pack Tactics. Amaruq 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. Amaruq has advantage on Dexterity (Stealth) checks made to hide in snowy terrain.

Innate Spell Ability. 3 times/day can cast the enlarge portion of enlarge/reduce on himself, concentration for up to 1 hour, giving himself advantage on strength checks and strength saving throws. Capable of carrying up to 8 medium creatures.
Bite (x2) reach extends to 10 feet, against one target (or two targets within 10' of each other) and his modifier becomes +16 to hit. Damage increases to 23 (2d12 + 10) piercing and a target creature must succeed on a DC 19 Strength saving throw or be knocked prone. Any medium or smaller creature reduced to 0 health in a bite attack is considered swallowed whole. Death saves will be automatic failures for every round a creature is swallowed. For the next 30 minutes, if enlarge is reversed for any reason (i.e. dispelled, reduced, broken concentration, etc...), any swallowed creatures will be forcefully expelled during the reduction phase.
Cold breath extends to a 30-foot cone and each creature in that area must make a DC 19 Dexterity saving throw taking 44 (8d10) cold damage on a failed save, or half as much damage on a successful one. 

Help. As a Free Action: Once per turn

Bite. Melee Weapon Attack: Twice per action, +12 to hit, reach 5 ft., against one target (or two targets within 5' of each other). Hit: 17 (2d10 + 6) piercing damage. If the target is a creature, it must succeed on a DC 15 Strength saving throw or be knocked prone.

Cold Breath (Recharge 5–6). Amaruq exhales a blast of freezing wind in a 15-foot cone. Each creature in that area must make a DC 15 Dexterity saving throw, taking 36 (8d8) cold damage on a failed save, or half as much damage on a successful one.

Teleport (Recharge 4–6). The dog magically teleports, along with any equipment it is wearing or carrying (including riders), up to 120 feet to an unoccupied space it can see. Before or after teleporting, the dog can make one bite attack.