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 attack rolls 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.

Natural Armor.  (Natural Talent, Lv2) Ymris gains a +1 to AC.

Ability Score Increase.  STR +4 (Lv4, 12, 14)  DEX +2 (Lv8)

Charge.  (Companion Tactics, Lv3)  If Ymris moves 20' to attack a creature, Ymris gains advantage on his next attack.

Fast.  (Companion Tactics, Lv13) Ymris' base movement speed is increased by 10' (to 50').

Bite. Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 7 (3d4 + 5) piercing damage (already modified for Brutal below). If the target is a creature, it must succeed on a DC 11 Strength saving throw or be knocked prone.

Extra Attack.  (Lv5) When Ymris takes the Attack action, he make make an additional attack.
Brutal.  (Offensive Tactics, Lv11) Damage on a successful hit is increased by 1d4.  As well, an unmodified roll of 19 or 20 will result in a Critical Hit.

True Ally.  (Lv6) Ymris can use his action to stabilize fallen creatures.  To do so, he must succeed on a DC 10 Survival check.  How Ymris does this is left to your creativity.  As examples, he may lick the wounds or attempt to move a contorted, unconscious body into a more natural position.

Protective.  (Companion Tactics, Lv7) When a creature Ymris can see within 5' attacks a target other than him, Ymris may use his reaction to impose disadvantage on the attack.

Uncanny Dodge.  (Defensive Tactics, Lv15).  When an attacker that Ymris can see hits him with an attack, he may use his reaction to halve the damage against him.