White Stag
White Stags or White Harts figure into the mythology of several different European cultures. They have appeared several times in D&D, usually as servants of a nature deity.
Fiend Factory
The White Hart appeared in White Dwarf #63's Fiend Factory as a nature spirit that appears whenever red deer are being endangered by creatures with human level intelligence. It always appears in the center of the herd and charges at the assailant, attacking with antlers and hoofs. It is immune to magic and cannot be truly killed; whenever it reaches zero hitpoints it simply teleports away. It wears a plaited gold rope around its neck given to it by Silvanus, the Celtic god of nature. Anyone who touches the rope is confused for 14 rounds. Striking the rope with a weapon deals 1d8 damage to the attacker and causes the white hart to teleport away. This rope is rumored to be the source of the hart's powers.
Forgotten Realms
Appearing in the 2e Forgotten Realms splatbook Elves of Evermeet, The White Stag is a unique servent of Labelas Enoreth, the elven god of longevity. It is larger than a normal deer, and has glowing red eyes. It appears wherever elves are in need of guidance or wisdom, and leads them to a place where a divine vision or message is given.
Pathfinder
The Grim White Stag is the herald of Erastil. It once was a god in its own right, worshipped by early druids, but once Erastil's faith became more prominent, it allied with him. It appears as a huge deer made entirely out of twisting tree branches.
