the perfect stalker

Item#:SCP-xxxx
Object Class:Keter
Special Containement Procedures:SAS
Description: SCP-xxxx is a species of predators that targets only humans with an unstable mental and/or psychological condition. SCP-xxxx, in all known cases, hunts one person at a time, becoming visible only by the chosen victim. The hunted person will also gain the ability to see others specimens of SCP-xxxx, but the creatures will ignore him/her, focusing only on haunting the chosen prey.
The life cycle of SCP-xxxx is yet partially unknown, but the first stage observed is a cocoon, composed of a biological material similar to spiderwebs, of the lenght between 2 and 5 m. In this part of SCP-xxxx's life, the creature is visible by everyone, but animals will stand away from it. SCP-xxxx will produce the cocoon only after the chosen prey is eaten, implying that the human subject is necessary to give the cocoon energy to sustain itself.
SCP-xxxx will enter the second stage only when a human with mental conditions enters in close proximity with the cocoon. SCP-xxxx will awake, changing its appearance in the way that creates the most dfiscomfort in the victim. This process can take between 5 and 15 minutes, based on known cases. Then, SCP-xxxx will exit the shell, causing terror in the prey. It is unknown if the specimen of SCP-xxxx that exits the shell is the same specimen that created it, or a newborn. Either way, SCP-xxxx will not attack its prey in this first encounter, leaving the victim free to run away. After this first time, SCP-xxxx will follow and toy with the chosen person in a behavioral pattern similar to felines, causing distress but not killing the victim.
When the prey will try to counterattack, or to escape the cycle of torment, SCP-xxxx will enter the third stage, the violent one. It will stop toying and haunting the target to physically attack him, trying to consume him/her. SCP-xxxx will only interact with other humans if forced, killing anyone who could see the death of its victim or who could be a threat or an obstacle to SCP-xxxx's will. SCP-xxxx will not eat its victims, outside from the primary target. When its target is consumed, SCP-xxxx will enter the first stage, and create a new cocoon.
The Foundation has captured alive only one specimen of SCP-xxxx, nominated SCP-xxxx-Alpha, which is currently "connected" with Doctor Kevner, supervisor at the Biological Containment Units at Site-██, where SCP-xxxx-Alpha is currentlty stored. Doctor Kevner is also the supervisor of all experiments made on SCP-xxxx-Alpha, and the responsible for Project "Manhunter", started at date ██/██/2009, and it has currently classified 1█ cases of SCP-xxxx.
Addendum 1:Discovery,capture and studies of/on SCP-xxxx-Alpha
SCP-xxxx-Alpha made first contact with Doctor Kevner while he was on a vacation in [DATA EXPUNGED] for mental heath recovery, after the containement breach of SCP-████ and the events following the former gave him insomnia and depression.
On date ██/██/2008, while he was descending the stairs of the [DATA EXPUNGED] Hotel, he noticed that the door of the room 217 was open, and that his occupant, [DATA EXPUNGED] was not in there.
After checking if the occupant was in the nearbies, Doctor Kevner decided to control the inside, finding the shell of SCP-xxxx-Alpha. Doctor Kevner then entered in conctact with the SCP-xxxx-Alpha, becoming the taget prey of the creature. SCP-xxxx-Alpha destroyed the shell, showing itself to Kevner in a form that personnel is not permitted to call "White Stalker".
This form resembles an octopus, covered with a pale, wrinkled skin, with 5 legs and a large head similar to the one of a "grey alien", with 1 single black eye with a red pupil and a large mouth resembling a smile. The smile is only aesthetic, and the real mouth is located between the legs, in a manner similar to sea stars and octopusses.
When SCP-xxxx-Alpha tries to eat its prey, 10 red tendrils, composed of a gelatinous substance, will exit from the mouth. These tentacles can reach the length of 7 m, and they can lift weights of 100 kgs without damaging the tissue.
As expected, Kevner ran away from the room, only to find SCP-xxxx-Alpha later in his bedroom.
From then, SCP-xxxx-Alpha stalked him for 4 days, until he conviced himself that he wasn't crazy, when he read the diary of the last victim of SCP-xxxx-Alpha. The diary, found in room 217, is now stocked in the Library of Site-██. Based on its personal observations and the notes of the precedent target, Doctor Kevner explained the situation to the Foundation, and asked for help. A Mental Health Test, and the administration of [DATA EXPUNGED], confirmed that he was not lying. The Capture Procedure took place in the hangar of Site-██, where Doctor Kevner shot to SCP-xxxx-Alpha, causing its rage. He then attracted the specimen inside a Biological Containment Unit, before exiting the cell from a secret passage. In this occurrence, air movememnt sensor perceived a speed of 35 km/h, and the floor was covered with scratches as deep of 5 cm. From then, the specimen never left the cell.