Charge. 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) damage. If the target is a creature, it must succeed on a DC 14 Strength saving throw or be knocked prone.
Actions
Ram. Melee Weapon Attack: +6 to hit, reach 10 ft., one target. Hit: 11 (2d6 + 4) bludgeoning damage.
Hooves. Melee Weapon Attack: +6 to hit, reach 5 ft., one prone creature. Hit: 22 (4d8 + 4) bludgeoning damage.
RollQuest summary Senses: passive Perception 14. Languages: Giant Elk, understands Common, Elvish, and Sylvan but can't speak them. Skills: Perception +4. Speed: 60 ft.
RollQuest ships the D&D 2014 SRD as a content pack, on a 5e character sheet that does the maths - roll from the sheet and let the numbers work themselves out. Free to start.