The Darksign is the sign of an accursed Undead.
The Darksign returns its bearer to the last bonfire rested at, or the bonfire at Firelink Shrine, but at the cost of all souls held.
Carriers of the Darksign are reborn after death, and eventually lose their minds turning Hollow. And so it is they are driven from their homelands.
Used to return to the last bonfire you rested at, or Firelink Shrine, at the cost of losing all your souls.
Automatically given to you at the start of the game.