Doomed timelines are a phenomenon in Sburb based on the fact that many events are the result of closed time loops. A doomed timeline is created when a person fails to do what they are supposed to do causing the entire timeline and its inhabitants to be doomed. Interaction between doomed timelines and other universes is prevented; however a person can travel back in time from the doomed timeline and avert the timeline ever being created. In fact this is at times necessary to succeed, meaning a doomed timeline has to exist in order to ensure its own non-existence. Players from doomed timelines can also send their memories back to their past selves on the alpha timeline. This is accomplished by going to sleep before the doomed timeline is erased. It is possible because, according to Dave, dream selves operate somewhat outside the normal time continuum, allowing memories from alternate timelines to be passed on.
Players that die in doomed timelines can appear in dream bubbles within the Furthest Ring. Doomed players who enter the alpha timeline also appear in dream bubbles after they die. Players that are still alive when a doomed timeline is erased do not seem to enter dream bubbles, as they cease to exist.
Three doomed timelines have been shown in the kids' session. However, there were likely others due to Dave's remarks about dead copies of himself. It is also possible that if that timeline did not affect the alpha timeline, none of the alpha players would be aware of its existence, and it would therefore have no bearing on the story. Of the three known, two were directly caused by Terezi. This stands to reason, as she is a Seer of Mind, and her role is to explore various possible outcomes.
The first brief one occurred when the Draconian Dignitary didn't receive any resistance to the theft of Rose's journals. Dave then traveled back in time to prevent the theft. DD killed that Dave, and seeing his body warned the alpha Dave not to repeat the mistake.
The second and most important one was created when John, under the guidance of Terezi, prematurely met Typheus and was killed by him. This indirectly affected the timeline in numerous ways. For example, John would no longer be able to perform the ectobiology needed to create himself, his friends and their guardians or function as Jade's server player. This would, in turn, prevent Becquerel's prototyping and prevent Jack Noir from becoming a threat to the trolls which would lead to them not trolling the kids thus not tricking John into prematurely meeting with Typheus. Alternate Future Dave originated from this timeline and prototyped himself, believing that the kernelsprite's preference for dead or doomed things would save him from death. Additionally, the Rose of this timeline was able to transfer her memories to her alpha timeline self, causing the awakening of her dream self.
The third doomed timeline was also created under the guidance of Terezi. She flipped a coin and made Dave decide which side of the coin would lead to him learning how to get to god tier immediately, and which side would delay the revelation. The flip itself was a constant across all timelines, but two alternate timelines were created by Dave's two possible choices. The Dave who chose "immediately" fell asleep on his Quest Bed, while the other, who chose "later" was eventually sent back in time to kill him. However, he was unable to go through with it, even though he knew that self was not from the alpha timeline, and was therefore doomed. The doomed Dave was killed by Jack Noir a little while later.
The Trolls' session was plagued with at least a thousand doomed timelines, Karkat blames himself for. However the army of Aradiabots produced by these ended up being critical in the fight against the Black King.
Interestingly, part of the genetic code found in First Guardians that was needed to create Doc Scratch came from a doomed timeline. In this doomed timeline, created when Karkat did not run the Mobius Double Reacharound Virus, Gamzee killed all of the trolls and wrote his part of the code in Karkat's ~ATH manual. The Aradia from that timeline brought the book back with her and somehow ensured the version from the alpha timeline would be destroyed in the explosion of Karkat's computer. The alternate timeline version of the book was later stolen by Agents of Derse to create Doc Scratch.
Another doomed timeline seen was the result of Terezi being unable to bring herself to kill Vriska. In this timeline, Terezi allowed Vriska to leave the troll's meteor to fight Jack Noir. However, Vriska left a scent trail from her wings, allowing Jack to find the meteor and kill the other trolls. When he had accomplished this, he returned to fight Vriska. The outcome of their battle is unknown, though Doc Scratch has stated he wouldn't bet against Vriska winning (were he a gambling man). This timeline was envisioned using Seer powers and Cue Ball-granted omniscience, and so may have only been a potential timeline as opposed to an actual doomed timeline. Aranea that this may not be the case, however, as she knows about it and that Terezi caused it but is not a Seer.
While traveling through The Furthest Ring, the characters on the meteor encounter other trolls that died in doomed timelines. Some of these trolls had attained God Tier before they died, including an alternate Feferi, an alternate Eridan, an alternate Tavros, and an alternate Karkat.
Pre-scratch Trolls' sessionEdit
Despite the pre-scratch troll session having a glitch that rendered the null session, leading to them scratching their session, the session, like its post-Scratch counterpart, had a large number of doomed timelines. Alternate Damaras from these timelines were hinted to have sabotaged the alpha timeline, suggesting that the doomed timelines may have had some degree of success. However Damara's sabotage was hinted to not be an attempt to preserve the alpha but rather out of spite due to the actions of Rufioh, Horuss and Meenah.