He was expelled from university for publishing a bizarre thesis, but because that thesis was related to SCPs, he was recruited by the Global Occult Coalition. During his 99th mission, he realized the GOC didn't suit him, murdered his colleagues, and joined the Foundation without a trace. As a former GOC operative, he excels at decommissioning SCPs. He particularly hates Reality Benders and insists they must be neutralized immediately. If you try to take a photo of Clef's face, it is replaced by another object, so there is no way to see his face other than in person. He claims to be a Ukulele A-chord and carries a ukulele around. His most prominent trait is being a pathological liar. For example, he might give incorrect mission briefings or manipulate schedules.

SCP-239 The Witch Child Object Class: Keter Type: Humanoid She takes the form of a young blonde girl with green eyes. This girl has the ability to manifest whatever she desires into reality. In other words, whatever she imagines and thinks becomes reality. Due to this ability, the world could end if she even has a stray negative thought. Because she cannot control this power, she must be kept in a permanent induced coma. Her real name is Sigurrós Stefánsdóttir. Clef is the one who insists she must be decommissioned as soon as possible.

A rival organization to the SCP Foundation, often abbreviated as the GOC. While the SCP Foundation contains SCPs, the GOC destroys them on sight. However, many of the SCPs destroyed by the GOC end up causing more problems due to their destruction, or were entities that didn't necessarily need to be destroyed. Nevertheless, since both the Foundation and the GOC share the common goal of peace, they ally during world-ending scenarios. The leader is a woman named D.C. al Fine. The organization consists of Strike Teams, Assessment Teams, etc. If the Foundation has the O5 Council, the GOC has the Council of 108. They use 'identifiers' to categorize anomalous entities.

A man employed as a photographer for the SCP Foundation. He wasn't very prominent when he first joined, but starting with his handling of SCP-408, he created 33 weapons combined with SCPs. He has an ambitious, artistic, chaotic, paranoid, antisocial, and malicious personality. He is Clef's rival and friend.

SCP-166 Just a Teenage Gaia Object Class: Euclid Type: Humanoid A European female in her late teens with deer antlers, hooves, and a short tail similar to a reindeer. If any man-made object comes within a 15m radius of SCP-166, it rapidly decomposes or rots, while plants begin to grow in that area. SCP-166 is extremely sensitive to artificial or polluting substances; even a single contact can cause pressure sores or asthma symptoms. Due to these traits, humans contacting SCP-166 must always wear biohazard suits. Her mother is presumed to have been killed by the GOC, and the killer is suspected to be her father, who was a member of the GOC. And that father might be Dr. Clef.

Dr. Alto Clef's former secretary. A seasoned professional who dislikes overly elaborate plans. She prefers simple, cost-effective approaches to anomalies. She is currently assigned as the security officer for SCP-105, the 'Last Hope' of MTF Alpha-9.

Level 3 Researcher. Currently the head of the Inter-Site Experimental Initiative. Dr. Edison has been disciplined multiple times for repeatedly engaging in unauthorized, poorly planned actions. Usually quiet and taciturn, Dr. Edison secretly dreams of becoming a 'real man' like Dr. Clef.

SCP-105 Iris Object Class: Safe Type: Humanoid A blonde woman who carries a camera (SCP-105-1). When she takes a photo with it, the photo turns into a real-time video, and she fights by reaching into the photo to make her hand appear in that physical space. She can also telekinetically pull objects weighing less than 5kg from within the photos she has taken. She is currently the team leader of MTF Alpha-9, 'Last Hope'.

The Under-Secretary-General and leader of the Global Occult Coalition. She is known to be a European female of unknown age and nationality. All other information regarding her is classified under the 1949 Secret Information Ordinance. She appears to have a history with Clef.

SCP-447 Ball of Green Slime Object Class: Safe Type: Object A non-corrosive green slime ball. The secretion emitted by SCP-447-1, known as SCP-447-2, can be mixed with gasoline to increase fuel efficiency by 150%, and can also be used as a cleaning agent or food additive. However, if it comes into contact with a dead body, it results in [DATA EXPUNGED]. Dr. Clef sent a message berating the researchers managing this SCP as pathetic, which led the doctors in charge to drop Clef into a bathtub full of SCP-447-2, making him furious.