|“||There are rooms in the building where other dimensions leak in. We call these rooms 'Thresholds.'||”|
–Zachariah Trench, Control world trailer
Thresholds are locations acting as connections between Earth and other dimensions, which come about as a result of paranatural phenomena. Within the Oldest House, Thresholds appear spontaneously and are under continuous study by the Federal Bureau of Control, with Bureau agents known as Rangers responsible for performing reconnaissance and investigation of the internal topographies of Thresholds.
Thresholds are believed to occur as a result of the resonance frequencies of other dimensions aligning with Earth's, thus resulting in the creation of locations which act as bridges between these dimensions. While the Oldest House is a frequent site of Threshold emergence, other locations on Earth have developed Thresholds as well, such as Cauldron Lake in Bright Falls, Washington. Within the Oldest House, Thresholds often appear without warning, with some being relatively stable and long-lasting, and others being only momentary. The Black Rock Quarry, for example, has existed for long enough for the Bureau to establish a permanent presence within its respective dimension; the Mold Threshold, meanwhile, emerged shortly before the Hiss invasion and posed a major threat to the Bureau until Jesse Faden defeated Mold-1.
Thresholds lead to other realms referred to by the Bureau of "dimensions," but the actual nature of these dimensions is unknown, with many competing theories existing within the Bureau. Some believe they are parallel universes, while others consider them to be Earth's dimension at different times or locations. One theory suggests that Earth itself is a Threshold leading to the Oldest House, though this opinion causes unknown maladies in those who suggest it, leading to it being actively repressed. The Bureau investigates the nature of Thresholds using agents referred to as Rangers, who are tasked with entering and surveying Thresholds - a respected and highly dangerous role.
In the Oldest House
- Cauldron Lake Threshold