Elk

An elk ally is a druid's wild shape, a ranger's animal companion in a homebrew setting, or the gift of a forest spirit who told the party "follow this stag and you will find the river." The framing that works best is the gift, because elk are not pets. They tolerate riders briefly, they bolt at sudden noise, and they will leave the party the moment the road feels wrong.

Mechanically, the elk is a 50 ft. mount that carries a Medium rider through terrain the party's horses cannot handle. Use it for one specific journey, not as a permanent acquisition. In combat, dismount the rider immediately. The elk has 11 HP and AC 10 and dies to a single hit from anything that matters. It will run when the violence starts, and will only return at the end of the scene if the party calls for it.

Out of combat, the elk is a Perception asset (passive 12, Darkvision 60 ft.) for night watches and a navigation aid in dense terrain. A druid PC can communicate with it via Speak with Animals to get one-line answers about what's downwind.

When the journey ends, the elk leaves at the treeline. If a player tries to keep it as a permanent companion, have it wander off on the third night when no one is watching. The point of the elk was the trip, not the pet.

An elk is wilderness texture, not a fight unless you build the encounter around it. CR 1/4, AC 10, 11 HP, it charges with Ram at plus 5 for 1d6+3 bludgeoning. If the elk moved at least 20 ft. straight toward the target, add another 1d6 bludgeoning and knock the target Prone. That combo is its entire offense.

Use an elk in three scenarios. First, the random encounter that isn't a fight: a bull elk on the trail in rut, antlers down, blocking the only path. Animal Handling DC 12, Intimidation DC 14, or detour. Second, the stampede: the party flushed a herd by being loud, and now the druid's bear and the rogue both need Dexterity saves not to get trampled while twenty elk run past at 50 ft. Treat the stampede as terrain, not enemies. Third, the wounded animal that injures someone careless: a hunter PC tries to finish a downed elk and takes a desperate kick, 1d6 damage and a lesson.

If you do run a solo elk as a combat encounter, it should be because something else is wrong. The elk has 50 ft. walk speed and no ranged option, so it closes fast but then stands there hitting one thing. It routs instantly. Wisdom 10, no traits, no immunities. A loud spell, a sudden fire, or a single drawn blade sends it running faster than the party can follow.

Don't make the players grind an elk. If you've put one in front of them, the answer should be roleplay or a single skill check. Save the dice for something that matters.