The Darkmare is a fiend/nightmare-type enemy from Final Fantasy XII. One can be found in the Ward of the Sword-King area of the Stilshrine of Miriam. When approached, it will teleport far behind the party, but will teleport back to the party seconds later.
Being a nightmare transformed by long years of living in lands saturated with Mist, preferring to inhabit ruins and other places starved of light. Mist rises in clouds about its body, and pours incessantly from its mane and hooves.
The Darkmare is one of several enemies that respawn only when certain conditions are met. Only one appears in the entirety of the game, in the Ward of the Sword-King in the Stilshrine of Miriam. In order to fulfill the required headcount to fill out the Bestiary, the player cannot repeatedly respawn the Darkmare by zoning over two areas (the trick for many other enemies).
Instead, a respawn can be forced by saving and then resetting, preferably at the save crystal in the neighboring zone, the Walk of Revelation, or by leaving the area completely (i.e. teleporting to another location and then teleporting back).