Vault 8166

Vault 8166 is a rumor related to several hidden servers or games on ROBLOX that is said to home several hackers and unusual occurrences. It is supposedly ran by unknown hackers, which have the ability to watch or monitor activity going on between users.

It is said that anyone who goes there can gain access to certain information on ROBLOX and use the Installations, GUIs, and programs. It is then used to create new software, bots, or viruses that are placed and hidden into ROBLOX models or plugins. When inserted into a place, they obtain the ability to interfere with gameplay, local scripts, and computer monitors.

Discovery
On November 15, 2016, an anonymous user posted a thread on the former ROBLOX Talk sub-forum. The user claimed to have entered an "unknown place" while testing out a teleporter for their game by accident. The thread was a brief summary on the dark side of ROBLOX and that there is a place where hackers are gaining access to user profiles and other information. This secret place was referred to as "Vault 8166". A few hours after the thread was posted, the word went out. However, the thread was nowhere to be found and it's OP (Original Poster) was never identified. The thread may have been deleted by moderators. If not, something else was at work, and it wanted it deleted.

Leaked Footage
There is leaked footage of an incident released on YouTube.

The footage features 2 humanoid figures walking down a hallway with alarms going off. One figure is lit on fire. As they walked down the hallway, the figure on fire stops and looks at a poster featuring a skeleton with the tagline, "WARNING: We are watching you". Suddenly, a creature comes running after the figure on fire just as it turns around. Just as the creature tackles the user, the footage blacks out in an instant.

This creature was identified as "The Dark Soul" or "W0AT". The fate of the 2 users have never been confirmed.

Trivia

 * The name "Vault 8166" is derived from the 1st four numbers of 1x1x1x1's user ID, 8166491.