Per 
Three instances of SCP-4483 seen under a subatomic microscope.
Special Containment Procedures:
All known instances of SCP-4483 are contained at secure Site-████ in ████████, Germany. All iterations of SCP-4483 are to be pacified via an UHF emitter, and placed in a fifty (50) by fifty (50) centimeter case constructed from Alnico alloy of no less than 10.5% Al, 20% Ni, 13% Co, 4% Cu, 0.5% Ti and 52% Fe. Case is to be magnetized and submerged in a five (5) by five (5) meter pool, filled brine water of 20% saturation. One sheep brain is to be placed inside the case, and replaced when white tissue loss exceeds 60% or higher. Chamber walls must be coated with a non-reflective hydrophobic material. Water salinity must be measured and if necessary, replaced bi-weekly by two D-Class personnel. Infected personnel or known victims are to be placed into an induced coma.
Description:
SCP-4483 is an anomalous species of subatomic organisms visually-similar to hexapods of the order Diplura. SCP-4483 ranges between 0.34 and 0.55 attometers, based on subatomic microscope observation, and are covered in a thin, heat-resistant cuticle analogous to tardigrade. SCP-4483 is capable of passing through solid objects with relative ease. It is not known specifically how SCP-4483 achieves this, as it cannot be reliably observed. Speculation from research staff has suggested a form of quantum tunnelling. SCP-4483 subsists on white brain matter, and will burrow into an intended victim's head, typically clustering around the amygdala.
As SCP-4483 feeds upon the surrounding tissues, victims will experience vivid hallucinations, which are for reasons unknown, capable of interacting with their surroundings, provided the subject is conscious. SCP-4483 are seemingly confused and disorganized when subjected to sufficient magnetic force, and may enter a lull state when submerged in saline fluid. It is hypothesized that SCP-4483 enters a quasi-state of hibernation brought upon by severe dehydration in an effort to self-preserve. Mobility is reduced in these instances to the point where containment is possible for a brief window of no more than three minutes, after which SCP-4483 will enter an aggressive state, and swarm the closest creature with sufficient higher brain function. Observation shows that SCP-4483 reproduces rapidly through mitosis, creating new instances of SCP-4483 during feeding, though will initiate mitosis when threatened.
Discovery:
SCP-4483 was discovered on November 9th, 199█ in Weimar, Germany. Living in isolated colonies in Ginkgo biloba trees around the city of Weimar, SCP-4483 was first noticed after a brief period of unexplained murders in the Holzdorf area. Foundation staff secured an individual suffering from a rare case of benevolent hallucinations. Subject described projected manifestations as akin to guardian angels who moved other potential victims to safety, while calling his unseen tormentors "Der Nachtmar". Scans of subject's brain revealed the present of SCP-4483 burrowing through the amygdala. Attempts to remove SCP-4483 resulted in increased loss of white matter. Subject expired within three days and was cremated at high temperatures, with the remains placed within temporary containment.
Currently, the Foundation believes SCP-4483 was either purposefully engineered, or is a xenoparasite brought to Germany via meteor. Research is underway to reproduce the effects seen in the Holzdorf Subject, and the potential benefits SCP-4483's manifestations may have for the Foundation.
