There are two types of Blood Stains within the game.
Dark Blood Stains
Like Demon's Souls and Dark Souls, these dark Blood Stains show the last few moments of a player who perished at that spot. You can examine the stain in order to observe a phantom of that player reliving their death. If you see one, be wary of traps, falls, and difficult enemies.
Glowing Green Blood Stain
This blood stain is left after your death in your world. It will be on the spot where you died. If you died by fall damage or by falling down chasms, the blood stain will be on the spot ~5 seconds before the time of your death. This contains all of the souls that the player had on them at the time of death. A second player death will cause the previous blood stain and its accumulated souls to disappear and a new blood stain with the number of souls contained at the time of that second death to appear.
Notes
- If a dark blood stain shows a phantom who gets parried the player will hear the sound that plays when landing a parry in their world. (This also happens with various other sounds, such as the bell sound played when hitting the Watcher's Shield.)
- Using the Darksign to kill yourself doesn't leave any blood stain nor erase any previous blood stain.
Scholar of the First Sin
- If there are many bloodstains in one spot, they will be called a "Pool of blood" and activating one will activate them all.
