Fog Door

, also known as Fog Walls, are found throughout the world of Dark Souls.

General Information
s act as a barrier between certain areas and are usually found before boss encounters.

Once passed through, it is impossible to use them in the opposite direction, in the case of boss encounters, but will disappear once the boss is vanquished.

Invasions
When being invaded, s will appear in the general vicinity to limit the staging area.

Locations

 * Northern Undead Asylum - Before the balcony, during the Asylum Demon encounter.
 * Undead Burg - Before the Hellkite Dragon is first spotted. Before the encounter with the Taurus Demon, as well as before the exit on the opposite end of the arena.