Stalkers

For a lot of people, walking alone at night is a terrifying experience. Even more so, if they think someone is walking behind them.
Those feelings of fear gave birth to the first Stalkers way back in humanity's past.
Before The Curtain has fallen, they were only a false premonition, when one turned around there was nothing there. But when the material and the spiritual world mixed together, those beings gained the ability to finally manifest themselves.

The Hunt

When the Stalker chooses their prey, the prey starts to feel as if something was looking at them. The feeling gets stronger and stronger until they finally turn around. That's when the Stalker shows up, around a hundred meters from them. It doesn't move when looked at, but wherever one moves, the creature will always be behind them. From now on, the hunt begins.
Every time one turns around, the Stalker will get closer and closer. It can only move a few meters at once, but with its every move, the compulsion to turn around gets stronger. So for someone with weak will, it will only close the gap.
When it is about 10 meters from their prey, it starts to crawl, as if ready to pounce. When it's 2 meters away, one can hear it's breath on their back, warm, wet and regular. It starts to make sounds one could compare to really muffled laughing underwater. Some say it's possible to discern some words in that sound.
But at this time, the need to turn around and look at them gets so strong, you can't even fight it.
And the next time you turn will be your last one.

Basic Information

Anatomy

When looked at from the distance, Stalkers look like shadowy humans dressed up in black, leathery coats. The only discernible part of their faces are their mouths, constantly morphed into a grin, showing their white teeth.
When closer, one can see that their coats are really their skin, similar to that of the amphibians. What seemed like the face covered in shadows turns out to only have markings that create an illusion of a face. Besides their mouths filled with teeth, their heads are completely smooth.

Growth Rate & Stages

As the Stalker feeds more, they get taller and more imposing. They also start to move more quickly during the hunt, giving their quarry fewer chances to not look back.

Additional Information

Perception and Sensory Capabilities

It is unknown if Stalkers perceive the area surrounding them or if they only can feel that the one they hunt is looking at them.
As with most spirits, all attempts to capture and dissect them have been proven unsuccessful as their body breaks apart turning into pure spiritual energy.

Origin/Ancestry

Fear

Reproduction:
As spirits, Stalkers do not reproduce in any way.

Habitat

Stalkers show up mostly during nights and only in the areas where humans lived.
They are solitary and territorial spirits, however, there was a rumor of two Stalkers hunting one prey, circling and flanking it.

Feeding

For Stalkers, the process of following their prey and causing them distress is the source of their energy.
Killing them is only a part of the ritual that gives them no benefits.
Even if the prey escapes, the Stalker probably won't run after them anymore, as it had fed already.

The Taboo

Stalkers can't get closer to someone unless their prey turns around, so if one can fight off the compulsion and don't look back, the Stalker will stop following them very fast, looking for an easier meal.
They also can't follow it if the quarry reaches the place they would deem safe (usually a building).
They can only follow one person at a time, so even if the said person is in the group, the Stalker will attack only one of them. Additionally, the friends of the hunted one can look at the spirit as much as they want. They won't perceive the moment it gets closer. Stalker just suddenly is in the place it wasn't before.