Per 
SCP-7051's current form
Item #: SCP-7051
Object Class: Safe
Containment procedures: SCP-7051 is to be kept in a standard storage locker in the lower levels of Site 42 next to the primary on-sight clinic. No personnel wearing anything that might be interpreted as a costume are allowed within 5 meters of SCP-7051, including but not limited to: undergarments meant for the opposite sex, mismatched name tags, false fangs, heavy makeup, colored contacts, or a uniform from a different department. This perimeter is to be marked by signage. This perimeter is increased to 50 meters for anyone who makes their own costumes, as they find the urge to use SCP-7051 much stronger, and will seek it out even when they are not aware of its existence. As SCP-7051 is otherwise inert, no further containment procedures are required.
Addendum 7051-1: SCP-7051 is authorized for use on transgender individuals who pass all prerequisite psychological testing. Subject is to be given half a set of undergarments matching their chosen sex and exposed to SCP-7051, which will morph to become the other half of the set. Modifications to hair color, skin color, eye color, height, age, ethnicity, and build/weight, are to be approved or denied at the discretion of the supervising researcher. Any attempt to use SCP-7051 to gain anomalous abilities is to be denied and reported.
Addendum 7051-2: SCP-7051 has been shown to cure bio-hazardous anomalies if applied quickly enough after a minor outbreak of SCP-████. It is to be moved to a storage locker next to the primary on sight clinic in case of emergencies.
Description: SCP-7051 is currently a red lacy 32D cup bra, following the use of Dr. ██████ to change sexes. As SCP-7051 is capable of shape shifting, 7051’s true form is not known, though it has been observed changing into a variety of pins, weapons, armor plates, dresses, undergarments, and other pieces of attire. When in the presence of someone in costume, especially a costume with a missing piece or accessory, it will change shape to become that missing piece or accessory. The subject will then be compelled to pick SCP-7051 up and add it to their apparel. Upon doing so, SCP-7051 will transform the subject into whatever they are dressed as, with some limits. This transformation is immediate, and permanent. SCP-7051 will then retain that form until it detects another costume. The appearance is always perfectly copied, but any supernatural abilities the costume was supposed to have will not always appear, and usually at partial strength. This correlates directly with costume quality, and the anomalous properties will often not fully manifest unless the costume was exceptionally crafted and/or handmade.1 Each subject can only use SCP-7051 once.
The mental state of the subject is not altered except after a fully empowered transformation, when they will take on the general personality, but not memories or specific quirks, of their costume.
SCP-7051 was retrieved from ██████ Comicon on ██/██/████, after passing between most of the attending cosplayers and a majority of the general visitors. The unaffected convention attendees were treated with class 1 amnestics and sent home, while the convention site was locked down and all subjects affected by SCP -7051 contained inside. Due to the convention being located in a high density urban center, the transformed were later moved to a remote resort purchased solely to contain them. Those affected range in classification from safe to keter, depending on what they were pretending to be and the quality of the costume.
According to a subject that was dressed as ███ ████, it purchased SCP-7051 from an onsite vendor, but could not describe the transaction in detail when pressed. SCP personnel are to scan conventions for further instances of SCP-7051, as ███ ██████ does remember the vendor having other objects for sale that might share SCP-7051’s properties.