Bouldertusk (young)

Trampling Charge. If the boulderusk 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 bonus action.

Gore. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 18 (2d8 + 2) piercing damage.

Stomp. Melee Weapon Attack: +4 to hit, reach 5 ft., one prone creature. Hit: 12 (1d10 + 2) bludgeoning damage.