Warstag

Trampling Charge. If the horse moves at least 20 feet straight toward a creature and then hits it with an antlers attack on the same turn, that target must succeed on a DC 14 Strength saving throw or be knocked prone. If the target is prone, the horse can make another attack with its hooves against it as a bonus action. Crit fails on the saving throw result in the enemy being dragged with the Warstag up to its full movement.

Antlers. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 11 (2d6 + 4) piercing damage.