The 9/11 manifestations is the term used by Ringbearers when referencing what is considered to be the single largest event of ghostly phenomena (known to the Corps of Ringbearers as Epheremals) in a specific location in Ringbearer history. The direct result of the September 11 Attacks as they occurred on 'Daria-404' in the Daria Multiverse, the manifestations have replaced the Borley Rectory manifestations (in this world, the events - and far more - actually did occur) and the Giza Necropolis manifestations in Egypt (also on this world) as the the most pronounced series of manifestations encountered to date, with every known form of spiritual manifestation witnessed to date occurring on the grounds where the attacks occurred.
In the history of 'D-404', the buildings of the World Trade Center were destroyed in the September 11 attacks, but were then rebuilt as they originally stood (as a rebuff of the terrorists who destroyed the site.) In this reality, over 10,000 people died on 9/11; also, the damage in this reality was limited to New York City alone, as the remaining planes struck the United Nations Headquarters (crashing into the General Assembly Hall) and the New York Stock Exchange.
While there were many reports of 'ghostly activity' on all three sites, such reports were either downplayed or dismissed as frauds until the re-opening of the WTC complex four years later - at which point the Twin Towers acted as a 'lens' of some sort that focused the energies of the souls of the deceased in the area and caused a backwash of energies that somehow stabilized the area encompassing Manhattan Island and formed permanent rifts which 'bleed' energy into the zone and allows spiritual activity on an indefinite basis. After the first month, literally tens of thousands of spirits were cataloged, and hundreds of thousands of activity reports were filed - including tens of thousands of reports of malicious and hostile manifestations.
The first Ringbearers appeared on D-404 about a year after the Manifestations began. The Ringbearer presence on D-404 is one of the largest Ringbearer forces ever gathered, and a permanent Citadel was constructed for them in Central Canada (on the shore of Hudson Bay in northeast Manitoba). The Ringbearers recruited many natives for Ringbearer status, and the threat of the Manifestations was ended three years after the Ringbearers' arrival. However, the world is still subject to all forms of spiritual intrusion, and the Ringbearers assigned there, along with the world's nations, keep a constant vigil. The Ringbearers also have one of the Mobile Advance Bases available on permanent assignment to that Earth; through successful diplomatic relations with the nations of this world, the Corps of Ringbearers is considered a nation-state, with the Mobile Advance Base and the Citadel afforded Extraterritoriality, and thus engages in trade relations with the planetside nations for goods, services and technological innovations (all treaties are cleared and approved beforehand by the Ringmasters, as per language in the Nova Valdris Accords. The Corps has also built a massive undersea Citadel (which is becoming the major point of Corps activity and influence - as well as a major tourism hub) in the Tasman Sea, roughly one hundred miles east of Canberra.
Any Ringbearer who asks has the option of being sent to the Ringbearer base on D-404 for a twelve-week enhanced course on supernatural detection and engagement tactics.
Danielle Todds was one of the first Ringbearers to detect the activity and set foot on D-404, and the Ringbearer known as Archangel was a member of the last Ringbearer force assigned to the 9/11 manifestations before the area was declared pacified.
D-404 is one of the worlds seen in the Corps of Ringbearers' recruitment video (as seen in the LLH fan fiction Consider The Corps).