Charge. If the yak moves at least 20 ft. straight toward a target and then hits it with a gore attack on the same turn, the target takes an extra 5 (1d10) piercing damage. If the target is a creature, it must succeed on a DC 12 Strength saving throw or be knocked prone.

Stubborn. The yak has advantage on saving throws made against being charmed or frightened.

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

Trample (1/day). The yak moves up to its speed and can move through the space of any creature of Large size or smaller that is in its path. Each creature in that area must make a DC 12 Dexterity saving throw, taking 14 (4d6) bludgeoning damage on a failed save, or half as much damage on a successful one.