The Sacred Timeline is the term designated to the collection of realities that were isolated after the Multiversal War by He Who Remains. These realities shared the same baseline despite being different from one another as they all only led to the birth of He Who Remains and thus, prevented the birth of evil variants of him.
Therefore, the Sacred Timeline followed a strict script, which meant their inhabitants did not truly have free will as if their choices caused a branch within the Sacred Timeline that deviated from the sacred path, the Time Variance Authority would arrive to prune it. These divergences received the term of Nexus Event. The TVA had to prune those branches before they reached a certain point of no return as after that the timelines could not be reset and the Multiverse would spiral into chaos.
Once the Multiversal War was brought to an end, He Who Remains isolated a certain collection of realities from the rest of the Multiverse. The realities he chose followed the same baseline, they all led to the birth of himself and only him, no other variants would be born from it. To protect this collection, the Time Variance Authority was created.
A Fake Story
- "But then, the all-knowing Time-Keepers emerged, bringing peace by reorganizing the multiverse into a single timeline, the Sacred Timeline. Now, the Time-Keepers protect and preserve the proper flow of time for everyone and everything. But sometimes, people like you veer off the path the Time-Keepers created."
- ―Miss Minutes[src]
He Who Remains then created the story of the Time-Keepers. The members of the TVA would believe that the Time-Keepers ended the Multiversal War, and then merged all the realities into one single timeline to prevent another war from happening. With their own barometer, the TVA was able to sense the realities that branched off and deviated from the Sacred Timeline's baseline causing a disruptive event, a new path that could lead to the birth of another variant of He Who Remains. When the reality was sensed, the TVA arrived to prune it. This divergence from the baseline received the name of "Nexus Event". However, there were some instances where the timelines created within the Sacred Timeline were not severe enough to be pruned and were either allowed to exist for a certain period of time or never be pruned. For example, Sylvie Laufeydottir and Classic Loki's timelines were both allowed to exist until the Nexus Event deviated those realities from the baseline. In the case of Classic Loki, his reality was pruned several years after the branch happened, which was Loki faking his death during the Attack on the Statesman, as the nexus event was instead Classic Loki trying to see his brother again.
Capture of L1130
During the Time Heist, the Avengers time-traveled to the past and created several timelines. This was all meant to happen, howsoever, the escape from a variant of Loki during the Battle of New York caused a Nexus Event in the Sacred Timeline. The TVA arrived, arrested Loki's variant and erased the reality. This variant, assigned to the name code L1130, was taken to the Time Variance Authority Office where he was judged by Ravonna Renslayer. Before he was sentenced to be pruned, Mobius M. Mobius intervened for him. L1130 finally opted to work for the TVA after witnessing how powerful the agency was that even the Infinity Stones were powerless inside their office. While his secret plan was to overthrow the Time-Keepers and control the TVA, Loki worked alongside Mobius to chase another variant of Loki.
Proving a Theory
As this evil variant was not so easy to capture, Loki saw a pattern in his variant's actions and noticed that the variant used apocalyptic events to hide the Time Travel effects within the Sacred Timeline, as the branches and their nexus events were not detected because the apocalyptic event erased all the changes. Loki and Mobius time-traveled to the year 79 before the eruption of Mount Vesuvius while Loki made slight alterations in the timeline, Mobius was shocked to see the divergence was not detected as this new timeline had not deviated from the Sacred Timeline's baseline.
Bombing of the Sacred Timeline
In her quest for revenge against the TVA, Sylvie Laufeydottir, the variant Loki and Mobius were chasing, who had stolen several reset charges from the Minutemen, planned a massive attack on the Sacred Timeline. Laufeydottir's plan was to drop all the reset charges in the Sacred Timeline to cause several branches and keep the TVA busy while she infiltrated their headquarters to kill the Time-Keepers. After a brief skirmish at an alternate 2050 in a Roxxcart Mall, Laufeydottir's plan was successfully executed, howsoever, she did not count Loki would pursue her. They both eventually got trapped in an apocalyptic event in Lamentis-1 frustrating Laufeydottir's scheme. The TVA then pruned all the branches in the Sacred Timeline restoring the harmony in the Multiverse a bit longer
An Unusual Nexus Event
Giving up on escaping their upcoming demise along with the destruction of Lamentis-1, Laufeydottir and Loki sat next to a lake. Due to them developing a strong bond with each other, a romantic one, they both holded hands, sparking a nexus event within their location. The Sacred Timeline suffered from the most rapid branch to have ever been recorded due to two variants of the same being falling in love. The Time Variance Authority detected the Nexus Event and arrested both Laufeydottir and Loki.
Freeing the Timeline
Sylvie Laufeydottir and Loki found the creator of the TVA, He Who Remains. At the Citadel at the End of Time, both Lokis were told of the truth of the Multiversal War and how the Sacred Timeline was scripted to follow a path where none other variant of He Who Remains would be born. While Loki wanted to take over He Who Remains' role to avoid the birth of evil variants, Laufeydottir did not trust what they were told and decided to kill He Who Remains. After a brief fight, Laufeydottir sent Loki back to the Time Variance Authority Office, she then killed He Who Remains. With his death, the Sacred Timeline was now allowed to have free will, multiple branches of the isolated realities began to branch off connecting with the rest of the Multiverse, allowing Kang the Conqueror to resurface and establish contact with the before isolated Sacred Timeline.
Kang got control of the TVA so he could manipulate the Multiverse at his will. Loki realized the TVA he was in was an alternate one to the one he knew as Mobius M. Mobius was receiving orders from Kang to let 63 branches happen. With the Sacred Timeline broken, and the Multiverse under the control of Kang, Loki could only watch in despair how they had made a terrible mistake.
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