Severance is the recurring symbol of the Slenderverse series TribeTwelve, and is later revealed to be a powerful entity.
HABIT reveals that the symbol commonly associated with the Observer (and, ostensibly, the Collective) is actually a rune of great importance and power. It symbolizes "severance", and acts as a separator between someone's or something's and a specific object—placing it on an object severs ties between that object and its owner or controller. It is stated that, in many cases, the Observer used this symbol to hack into Noah's computer and his various online accounts, by 'separating' them from Noah's control. HABIT explicitly states that applying the symbol to a weapon would turn it into something that would harm the Administrator, or at the least free Noah (and possibly the Collective) from the Administrator's control. It's possible, however, that HABIT is simply lying; even HABIT admits this may be the case.