Elk

Elk is a primarily green/white creature type used for cards depicting large deer. Elk (or Wapiti) are similar to the Red Deer found in Europe, of which they were long believed to be subspecies. In the deer family, only the common moose (confusingly referred to as "elk" in some European countries) rival the elk in size.

History
The first creature to bear the type was Gang of Elk from Urza's Legacy. It used to be a Beast, but this was changed in the Grand Creature Type Update. For a long time, it was the only Elk card until Great Sable Stag was printed in Magic 2010. Theros features an enchantment creature with the subtype that acts as Heliod's Emissary.

Winged elk-like elementals embody white mana in Lorwyn–Shadowmoor, like Purity and the steed of the Archon of Justice.

Arcavios
The Cervins of Arcavios feed on the mana-rich plants around the star arches, imbuing their bodies with extraordinary grace and vitality.

Shadowmoor
The Cervins of Shadowmoor are long-legged, deer-like mount used by the higher ranks of Gilt Leaf hunters. Prized for their beauty and gentle temperament, cervins remain calm during combat. They roam wild in the Gilt-Leaf and are easily trained, but elves prefer to ride a pure-bred domestic over a wild-born animal. When breeding cervins, the elves track bloodlines, and the most perfect mounts are gifts to the most perfect elves. Some elves who are lower in the social hierarchy ride vinebred cervins because they're deemed more acceptable than riding a flawed cervin.

Oko
The planeswalker Oko can transform himself, a creature or an artifact into an Elk (Kenrith's Transformation, Oko, Thief of Crowns)

Trivia

 * Elk are Deer but not all Deer are Elk. That knowledge does make Mark Rosewater willing to change Elk to Deer if R&D would start over.
 * If the subtype would have been Deer instead of Elk, other species like Caribou, Moose, Fallow Deer and Roe Deer could have been included.
 * Deer was actually introduced as a creature type introduced in Unstable and has only appeared on silver-bordered cards so far (Druid of the Sacred Beaker).
 * The blue aligned Wetland Sambar</c> from Khans of Tarkir is the only non-white, non-green elk seen thus far.
 * Sambar is a real species.