The first known instance of SCP-3217. Corresponding SCP-3217-A instance is at large.

Item #: SCP-3217
Object Class: Keter
Special Containment Procedures: All non-profit organizations which operate within the United States of America are to have outgoing mail screened for SCP-3217 instances. In the event that a name on a piece of junk mail does not match any individuals residing at the relevant address, it is to be incinerated under the assumption that it is an SCP-3217 instance.
Due to the wide variety of anomalous abilities making individualized containment prohibitively expensive, SCP-3217-A instances in containment are to remain in chemically-induced comas in Site-17's Humanoid Containment Wing. Standard procedures for the care of comatose individuals are to be carried out.
Description: SCP-3217 refers to articles of junk mail delivered throughout the continental United States. Most aspects of SCP-3217 instances resemble solicitations from non-profit organizations such as the American Civil Liberties Union, the American Association of Retired Persons, or Greenpeace. A major discrepancy exists on all SCP-3217 instances, wherein the names of the individuals they are intended for are incorrect. The initials of the first and last name remain the same, but there is often little resemblance to the name of the recipient beyond this.
When opened by the intended recipient, that individual will become an instance of SCP-3217-A. SCP-3217-A instances develop one or more anomalous abilities, roughly corresponding to a theme consistent with the name printed on the SCP-3217 instance. Typically, SCP-3217-A instances will take on the role of vigilantes within their communities, using their abilities to fight what they perceive as criminal acts and moral or political corruption, as well as performing rescue operations. When committing these acts, they use the name on their SCP-3217 instance as an alias.

Damage from an energy blast caused by SCP-3217-A-45 ("Energy Exterminator", civilian name Edward Egel).

SCP-3217-B refers to a partial mailing list containing the names of 156 confirmed SCP-3217-A instances. SCP-3217-B was recovered from documents pertaining to the Manna Charitable Foundation's "Project Falcon", a defunct self-described "Local Hero Initiative" which was meant to encourage citizens to become more involved in their communities.
SCP-3217-B is heavily burned, due to a fire in Manna's Washington, D.C. Headquarters in late 2014, and appears to compile names from the mailing lists of over three dozen non-profit organizations, including the ACLU, AARP, the ASPCA, Greenpeace, the Southern Poverty Law Center, the NAACP, and the Horizon Initiative's F.L.O.C.K. Program1.
As demonstrated by SCP-3217-B, SCP-3217 instances are more frequently delivered to individuals with alliterative names (such as Felix French/"Firestorm Father", Kevin Kane/"Kid Kwake", and Douglas Dock/"Doc Danger") with 171 out of 262 contained instances targeting such individuals. Beyond this, there is no clear pattern in which SCP-3217 instances are distributed.
Addendum: Project Falcon: The Manna Charitable Foundation's Project Falcon was intended to be a world-wide political activism initiative, intended to "get people motivated to change the world and make everyone a hero in their own right".
This campaign had a mascot in the form of "Bright Falcon", a superhero in the form of an anthropomorphic peregrine falcon. Bright Falcon had several planned pieces of merchandise, including plushies, wristbands, and a comic book, "Bright Falcon and the Activists!".
Darryl Franklin, an amateur actor from the Washington, D.C. area, was intended to wear a Bright Falcon mascot costume at rallies and educational events throughout the D.C.-Virginia-Maryland area. Franklin and their family had been long-time donors to Manna, though it is unclear if they had knowledge of their anomalous activities.
Ultimately, Project Falcon was rendered defunct following the 2014 fire in the Manna Charitable Foundation's D.C. headquarters, which resulted in the destruction of critical resources needed to bring the project to fruition. Materials destroyed include mailing lists, scripts for the comic book, prototype merchandise, and a laptop owned by the project lead. Franklin himself was severely injured in the fire, as they were wearing the Bright Falcon costume at the time, and the foam head partially melted into their face.
Six weeks later, Franklin was reported missing from their parents' home in Ohio, where they had been recovering from their injuries. The first known SCP-3217 instance had been found on their desk, along with an incomplete suicide note, their father's revolver, and a black feather from a melanistic peregrine falcon.
Among the contents of the SCP-3217 instance was a note in Franklin's handwriting:

All of the best heroes have a tragic backstory that defines them.
Grow past that. Bright Falcon is dead.
Become the phoenix. Become Dark Falcon.

Continuing on the back with:

Yes, I know, mixed metaphors. You don't get any better at that in twenty years, sorry.

The result of SCP-3217-A-159 ("Captain Scarlet", civilian name Crystal Simpson) making contact with the feather delivered in Incident 3217-S17.

Addendum: Incident 3217-S17: During Site-17's monthly mail delivery, two-hundred and sixty-two SCP-3217 instances were discovered— one for each SCP-3217-A instance in containment at Site-17. Each of the SCP-3217 instances were empty, barring a single black feather; DNA analysis of the feathers has revealed that they belong to the same specimen of melanistic peregrine falcon which was delivered with the first SCP-3217 instance.
Testing revealed that when an SCP-3217-A instance makes contact with one of these feathers, [DATA EXPUNGED] leaving behind a burn mark in the shape of a falcon on the nearest wall. To date, no further SCP-3217-A instances have been recovered, routinely escaping Foundation containment attempts using similar feathers.

Footnotes
1. Food, Labor, Outreach, Care and Knowledge, meant to assist impoverished communities, both anomalous and non-anomalous.

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