The Darksign is an item in Dark Souls.
Granted to players from the beginning of the game.
Using the Darksign does not cause a bloodstain to appear; the souls and Humanity lost are permanent. Using the Darksign does not affect the previous bloodstain left by the player, which will still be available for reclamation.
It is almost never advantageous to use the Darksign. Death is usually preferable, as humanity and souls can at least be recovered. The use of Homeward Bone or the Homeward miracle also sends players back to previous bonfires, but without the penalty of losing souls and humanity.
Usage of the Darksign can, however, be occasionally advantageous. Since it does not cause previous bloodstains to disappear, it may be preferable to use it over dying if players are faced with a dangerous situation and do not wish to permanently replace their old, valuable bloodstain with a new and relatively worthless one. The Darksign can be used if a player is stuck through glitching or some accident that caused them to be trapped, and does not have Homeward or Homeward Bones at hand. Manual use of the Darksign also does not cause un-hollowed status to be forfeited the way death would, so it's viable to use it instead of homeward bone if the player has less than 500 souls.
The Darksign can also be used when being invaded, but also having a bloodstain to recover.