Trampling Charge - Triceratops

Monster Manual - 5e, D&D Basic Rules

Trampling Charge. If the triceratops moves at least 20 feet straight toward a creature and then hits it with a gore attack on the same turn, that target must succeed on a DC 13 Strength saving throw or be knocked prone. If the target is prone, the triceratops can make one stomp attack against it as a nonus action.