Elk

If the elk moves at least 20 feet straight toward a target and then hits it with a ram attack on the same turn, the target takes an extra 7 (2d6) bludgeoning damage.
If the target is a creature, it must succeed on a DC 11 Strength saving throw or be knocked prone.

Melee Weapon Attack: +5 to hit, reach 5 ft.. Hit: 6 (1d6 + 3) bludgeoning damage.

Melee Weapon Attack: +5 to hit, reach5 ft., one prone creature. Hit: 8 (2d4 + 3) bludgeoning damage.