What we know about the collapse of the Stargate (aka Aethergate) and the events surrounding it's collapse (First Aggeloi War)
Disclaimer: All current information and lore are from the closed beta test, which is subject to change before release. This post is primarily for people familiar with Arknights lore, but I'll try to explain some of the relevant background first for those who are unfamiliar with Arknights.
Terra is a planet and is the primary setting of Arknights. Many years before the start of Endfield, pioneers from Terra re-activated a dormant stargate on the northern fringes of the known world. This Stargate, referred to in Endfield as the Aethergate (stylized as Æthergate), was built by an advanced spacefaring civilization tens of thousands of years in the past known as the Predecessors. When the Terrans passed through the gate, they found themselves on a completely alien planet, known as Talos-II, the second moon of the gas giant Talos, and the setting of Arknights: Endfield.
According to officially released material, Terrans first stepped foot on Talos-II 152 years ago. It was also revealed, that the Aethergate has since collapsed and stranded the Terran colonists from their homeworld. It is mentioned that Terrans have survived on Talos-II for "well over a century" after the gate's collapse, suggesting the collapse occurred sometime between 100-150 years ago.
But what caused the Aethergate to collapse?
According to the Hongshan faction background, the Aethergate collapsed during the events of a war known as the "First Aggeloi War":
"The foundation of the Hongshan Academy of Sciences (HAS) was laid down by a surveillance team from Yan dispatched to Talos-II. During the few short hours after the First Aggeloi War broke out, these Tianshis had the chance to return to Terra via the Aethergate but they chose to stay and join the battle. This decision resulted in them being stranded on Talos-II with the other pioneers."
The OMV Dijiang background also confirms both events were related:
Humanity lost their lifeline to Terra when the Aethergate collapsed and the First Aggeloi War broke out. In the moment of despair against this sudden threat, human factions that included the UWST, HAS, and TGCC jointly initiated several research projects. OMV Dijiang was one of them.
Not a lot of information is available about the First Aggeloi War. The Aggeloi are hostile entities that predate the colonization of Talos-II. From what little knowledge is available, the entirety of the Northern Frontier was destroyed within the first 24 hours of this war:
"Humanity's history records described how the entirety of the Northern Frontier was destroyed within 24 hours after the First Aggeloi War broke out."
Where is the location of the Aethergate on Talos-II?
A line of dialogue from Perlica seems to indicate that the gate, like the one on Terra, is built in the polar north. Scenes from the special trailer also seem to support this. This would confirm that the Aethergate was lost within the first 24 hours of the war, since "the entirety of the Northern Frontier was destroyed within 24 hours".
What happened after the gate collapsed, and how did the war end?
The First Aggeloi War ended in a final battle that contaminated the First Originium, according to records related to the Reconveners.
"The First Originium crystal that traveresed the Aethergate to arrive at Talos-II was contaminated in the final battle of the First Aggeloi War."
According to Perlica, the Endministrator played a major role in leading humanity and ending the war.
TL;DR Summary
- Terrans arrived on Talos-II 152 years ago via the Aethergate
- 100-150 years ago, the First Aggeloi War broke out and the Aethergate collapsed
- The Endministrator led humanity in ending the First Aggeloi War
- After the war, those who remained on Talos-II became stranded and permanently severed from their homeworld, Terra.
BTW reading and collecting the info about all of this made me realize the true meaning of the title of the special trailer: Those Who Stayed. It's referring to those who stayed on Talos-II to fight and their descendants, as opposed to those who escaped back to Terra.
https://www.youtube.com/watch?v=H-rls7leIX8
Special thanks to u/DankaShu for compiling all of the in-game wiki entries and uploading them online for those without beta access: https://x.com/DankaShu/status/1880506532657525232