Per 
SCP-5978
Object Class: Euclid
SCP-5978 is a small pin that reads "Hidden". When the victim puts the pin on, they will be invisible to the world. They will see things other people don't see. While they are in this state, the beings in the realm know there existence. All of them are docile, but SCP-5978-2 is extremely aggressive. SCP-5978-2 will try to kill them when it sees them, well that's what we think. When the SCP gets to the victim, the pin will drop in the real world and the victim will never be seen again. The creator of the pin was ████ .
Testing:
The Class-D entered the cell and stood around the pin. Doctor Michael told the subjects to move forward. One of the Class-D put on the pin. After several minutes, the pin appeared outside its containment chamber. The guards put the pin back in the cell and the remaining Class-D Proceeded to put on the pin. After Several Hours of waiting, the Class-D appeared in the hallway outside of the chamber room in a shock phase. Doctor Michael took the subject to the interview room.
Interview:
Doctor Michael: "What did you see?"
The Class-D was still in a shock condition
Doctor Michael: "I said, what did you see!?"
Class-D: "I… saw….. things"
Doctor Michael: "What are those things?"
The Recording was buffering but we could make out "Sharp….Vicious….Bloodthirsty"
Doctor Michael: " Did it have Giant legs?"
Class-D "No, it was small, and fast"
Doctor Michael: "Did it try to kill you?"
Class-D "Yes, it got to me and climbed into my mouth"
Doctor Michael looked at the Class-D in confusion.
Doctor Michael: "thank you for your time, you can go back to the cell"
The recording buzzed and blurred. After several minutes, the footage came back on, and it showed the Class-D and Doctor Michael Dead. A black figure walked to the screen and the footage was over.
After the incident, the site had a massive containment breach. The omega warhead detonated and the monster was destroyed. The special trained MTF units went to the radiated site and found the pin still in its cell, unharmed. When they got to Site ██ the pin was contained in a 10 by 10 meter room made out of lead steel. Surveillance must be kept on it 24/7.
