Armoured War Cow

Trampling Charge. If the cow moves at least 20 feet straight toward a creature and then hits it with a horns attack on the same turn, that target must succeed on a DC 12 Strength saving throw or be knocked prone. If the target was knocked prone by a horns attack this turn or was already prone, the cow can make another attack with its hooves against it as a bonus action.

Celestial Resistance. The cow has resistance to necrotic damage.

Conductive Armor. The cow has vulnerability to lightning damage.

Milkable. A creature can use an action to attempt to harvest milk from the cow. To do so it must succeed on a DC 2 Animal Handling check or take 1d4 psychic damage. (If the creature attempting to milk the cow is hostile to it, the creature rolls with disadvantage and must make a DC 10 animal handling check to succeed.) On a success, one quart of milk is extracted from the cow. If this trait is used, this property of the cow can't be used until the next dawn.

Horns. Melee Weapon Attack; +4 to hit, reach 5 ft., one target. Hit: 12 (3d4 + 5) piercing damage. 

Hooves. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 11 (2d6 + 4) bludgeoning damage.

Moo to Arms. 3/day: The cow speaks a phrase in Primordial Bovine, attempting to rally animals to its support. Any non-hostile creature with a challenge rating less than 1 and a wisdom score less than 10 within 2d10 x 10 feet of the cow must succeed on a DC 10 Wisdom saving throw or becone charmed by the cow, as if under the influence of the Dominate Monster spell.

Bovine Affinity. If the cow suffers damage that does not lower the cow's HP below 1, it can use its Moo to Arms (with range of 3d10 x 5 ft. and save DC 6)