From 1d4chan

Werestags are one of three Good-aligned planar therianthropes created by fans of the Planescape setting for Advanced Dungeons & Dragons 2nd edition, and survive to this day in the netbook known as the Planescape Creature Codex. Their counterparts are the peganthrope and the werebunny.

These deer-like shapechangers inhabit the wild forests of the Upper Planes and are most commonly associated with the Beastlands and Elysium, although the Outlands also has one of the largest populations. Despite the name, there are female werestags, although in their original lore they are established as docile creatures that avoid all combat, leaving that to their protective male stag - like the deer they resemble, these creatures live in polygynous herds, consisting of a single male, his wives, and any immature children they have. As you probably expect, since this is a Neutral Good therianthrope based on a herbivore, werestags are both total vegetarians and devoted protectors of the natural order, something that makes them natural allies of druids and rangers. All werestags have the spellcasting powers of a 7th level Cleric, with access to the Spheres of plant, animal, weather, elemental, divination and healing. In addition to their obvious combat uses, werestags judiciously use their spells to aid the denizens of their chosen forest.

Werestags are full-fledged triple-form shapechangers, able to adopt the form of a majestic-looking deer, a half-elf, or an anthropomorphic deer. Vulnerable only to silver and magical weapons, they can summon giant stags to their aid (1d6, which arrive in 1d4 rounds) and attack with weapons, goring blows from their mighty antlers, and powerful strikes from their hooves, depending on which forms they are in. Male werestags also have the ability to unleash a kind of permanent Charm effect, which instills in the victim a deep-rooted fixation with protecting the forest, even if it means their lives - this knocks all the desire to fight the weresstag out of them, naturally. Weredoes lack both the antlers and the Charm power of their male counterparts, and so in combat they stay out of the way and focus on applying healing and buff spells to their champion instead. Werestags actually prefer to rely on their natural weapons over manmade ones, but some do carry them for when the need is dire - they prefer to focus on collecting magical defensive items, such as Amulets of Protection, which can bolster all three of their forms. They also move with great stealth in their native forests (Hide in Shadows 60%, Move Silently 40%), which allows them to easily avoid or ambush enemies.

Rarely, a white-furred and blue-eyed variant of the werestag will appear. These beautiful creatures are known as Ro'we amongst their kind and are always more powerful (usually with a +1 to Hit Die and abilities). It is said that they have been blessed by nature itself, and they are natural leaders and often become adventurers... but despite saying this, no rules for playing one are known to exist.

As well as having to deal with the usual suspects intent on wrecking their forests, werestags also have to worry about people coming after them for their horns. Aside from being potentially cool trophies, ground werestag horn is reputedly a powerful component in transformation spells. Naturally, they don't take kindly to people trying to get it.

The Therianthropes of Dungeons & Dragons
Laridian - Loup-garou - Loup du Noir - Lythari - Red Falcon - Seawolf - Selkie - Shifter - Swanmay - Thebestyn - Vodoni - Werebaboon - Werebadger - Werebat - Werebear - Wereboar - Werecat - Werecrocodile - Werefox - Werehyena - Werejackal - Werejaguar - Wereleopard - Werelion - Werepanther - Wererat - Wereraven - Wereray - Wereseal - Weresnake - Wereshark - Werespider - Wereswine - Weretiger - Werewolf
Antherions: Aranea - Song Dragon - Jackalwere - Wolfwere
Third Party: Werealligator - Wereanaconda - Werebunny - Werecheetah - Werecobra - Weremustela - Werepossum - Wereraccoon - Werestag - Werewolverine