History Timeline / Underverse

-->'''[=XFrisk=]''': "...Come on, brother! They're waiting for us."

* In one of the Genocide timelines in the original universe, Sans miraculously manages to kill Frisk while they were trying to deal with last blow, causing their timeline to be glitched into a Pacifist timeline. This results in him and Flowey remembering everything from that previous timeline, but for the rest of the monsters, including Frisk, to forget the past timeline, making him the owner of his timeline. Sans realizes the potential he has over the monsters and Frisk, but realizing the damage he may have brought, he confesses everything to Frisk, and the two of them (including allegedly Chara) bring themselves forward to Flowey and eliminates him.

* In desperation to continue saving dying universes, Ink ventures into an endangered universe to prevent this universe's Gaster from destroying all that he had created by showing him the multiverse. This Gaster feels motivation to continue to venture forward with his own universe, for his and their children's sake.
* '''TIMELINE I''': Now rechristened as [=XGaster=], he begins his experiment by giving his children, [=XTale!Frisk=] and [=XTale!Chara=], a family and friends to bond with. However, his perfectionism starts to show, and reluctantly overwrites this timeline altogether.
* [=XGaster=] takes an opportunity to showcase to Ink his unique ability: the OVERWRITE button, a power that grants the user the ability to change anything. Unwilling at first, Ink decides to allow [=XGaster=] to continue with his experiment, knowing that it would not affect the truce that he made with Error.

* '''TIMELINE II''': [=XGaster=]'s children start to get annoyed over the repetitiveness of this timeline, having to repeat their greetings with their friends and family. Eventually, [=XChara=] bonds over with [=XTale!Asgore=], while [=XFrisk=] shares a connection with [=XTale!Sans=]. This euphoria upsets [=XGaster=], prompting him to kill [=XAsgore=] and [=XSans=] in order to feel a sense of happiness. With nothing left to do, and with little resistance from [=XChara=], [=XGaster=] overwrites this timeline.

* '''TIMELINE III''': By far the shortest timeline that is overwritten, [=XGaster=] tries to replicate the features of another alternate universe, Underswap, to which he is dissatisfied with the results. [=XChara=] calls him out as an "insecure old man".
* '''TIMELINE IV''': Still hoping to stand up for Ink, [=XGaster=] attempts to begin a Genocide Route with [=XFrisk=], curious if his determination will ignore his order. His route is sabotaged, as his assistant [=XTale!Alphys=] sneakily reveals info to [=XTale!Muffet=] about this timeline, which leads her into convincing [=XChara=] to rebel against [=XGaster=]. He does so by utilizing the first instance of the RESET button, angering [=XGaster=] on the premise that the RESET button will cause other timelines to coexist.

* '''TIMELINE V''': Not wanting to leave his children without consequence, [=XGaster=] causes everyone in the [=XTale=] universe to forget [=XChara=] and [=XFrisk=], invoking their ire against their father. They attempt to get [=XAlphys=], their father's assistant, to spill the beans, but are put on a hold when [=XTale!Undyne=] stops them in their tracks. After hearing about their situation though, [=XTale!Undyne=] agrees to put the both of them under her belt for training, although [=XFrisk=] shows signs of resisting to go against their father. [=XUndyne=] and [=XChara=] confront [=XGaster=] directly, where [=XGaster=] had already eliminated [=XAlphys=] for her deceptive behavior, and orders [=XUndyne=] to hand him their child back. When she refuses and takes him down, he ends up overwriting [=XAlphys=] and the other anomalies from the previous timelines to take the two of them down.

* '''TIMELINE VI''': Weak yet willing to fight his father, [=XChara=] tries his hardest to take down his father's anomalies, but being unable to kill them, he's immediately taken down and half of his determination is swapped out for [=XGaster=]'s perseverance, granting him the power of the OVERWRITE button and kick-starting the X-Event experiment.

* '''TIMELINE VII''': Although disappointed with his newly obtained power, [=XGaster=] feels satisfied to have a fragment of determination within his soul. As his X-Event prototype repeatedly kills [=XFrisk=] though, he understandably sees this timeline as a waste of time, and is about to eliminate [=XFrisk=] altogether before his X-Event prototype convinces him that without [=XFrisk=], their souls are not satisfied. With this, the X-Event merges together with [=XFrisk=], where now his vessel is served by the X-Event's soul.

* '''TIMELINE VIII''': With both humans now inhabiting a single body, the X-Event is taught by [=XGaster=] on how to use the OVERWRITE button. The X-Event soon discovers [=XTale!Mettaton=] discarded within the data compilations, and managed to spring him into life. [=XGaster=] is immediately amused that his experiment can manage their own creativity, but despite this, he orders the X-Event to destroy [=XMTT=], invoking the wrath of X-Event!Chara and causing [=XMTT=] to nearly take him down.

* In fear that the X-Event and his creation would kill him for the consequences he has done to them, he asks Ink to carry half of his soul in a vial and stay far away until he begins his "third phase" of their game, explaining that he'll be able to handle himself with [=XChara=]'s determination.

* '''TIMELINE IX''': With only [=XChara=]'s determination by his side, [=XGaster=] is barely about to do anything but stare into the outside world. In a act of desperation, the X-Event tries to reason with [=XTale!Papyrus=] about [=XGaster=]'s evil acts, but the result causes him to lose faith in not only [=XGaster=], but the X-Event too. [=XGaster=]'s ruthless manipulation causes the X-Event to reset the timeline entirely.

** After breaking the barrier due to [=XGaster=]'s manipulation, the X-Event had tried to use the OVERWRITE button on humans to try to attack them as a way to provoke [=XGaster=] into trying to use his OVERWRITE button, however the will of their "friends" ends up ruining their plot and only enforces heavy surveillance by the royal guards, of which [=XSans=] ends up joining alongside his brother.
** Ten years after their first attempt at overwriting humans, the X-Event confesses to [=XSans=] over their current situation and how he feels trapped being monitored by a royal guard. [=XSans=] confesses that him joining the royal guard was to allow him to be closer to his friend, offering a sign of hope to the X-Event's goal.
** While transporting the X-Event around town, [=XUndyne=] takes the X-Event under "captivity", prompting a chase down to get their friend back. In the midst of this however, [=XSans=] is overwritten briefly and nearly goes forward to kill the X-Event had [=XPapyrus=] not intervene.
** The next day during the peace ceremony, he is overwritten once more to kill the X-Event once again with his Gaster Blaster, but [=XGaster=] promptly shuts him off. In a fit of anxiety, he tries to confess to [=XPapyrus=], [=XMTT=], and [=XAlphys=] about what's going on, but [=XGaster=] ends up resetting the timeline much to his fragile body.
** Later, the X-Event shows to [=XSans=] the original universe and how it differs to the current situation at [=XTale=], explaining that if they don't kill him, they won't see a future where they can make mistakes and create more timelines, and where he'll be the one in control. [=XSans=] does not agree with the X-Event's motivates, prompting a fight against the two where the X-Event finishes him off with the OVERWRITE button. Feeling sorry that he ruined his dress, the X-Event clarifies that once this timeline is overwritten he'll nickname him Cross, and that he'll create something better than what [=XGaster=] has done.
** Now fully recovered from resetting previously, [=XGaster=] ends up stopping the X-Event in its path and resets the timeline itself, which to his dismay revealed his sole determination half and with the implications that the X-Event has the only control of the OVEWRITE button. With this knowledge, X-Event!Chara suggests to his brother to bring back their friends' memories and then to kill [=XGaster=].

** Displeased that Cross is still unwilling to accept the X-Event's offer, [=XUndyne=] and [=XPapyrus=] end up beating Cross down, in light that he would interfere in their business to take down [=XGaster=]. Cross survives, and decides to take things into this own matters.
** During the confrontation between [=XGaster=] and the X-Event, Cross intervenes and kills the rest of the monsters, including his brother [=XPapyrus=], in order to take the X-Event as his own. In doing so, X-Event!Chara tries to take over Cross' body to reunite with X-Event!Frisk, but Cross takes his vessel out with his knife, resulting in X-Event!Chara being stuck under Cross. Only then does Cross realizes that the X-Event's power were incompatible with his monster soul, making him unable to bring back his friends in the process, and causing him to mentally break down.
** [=XGaster=] survives the ordeal, now outside his own universe. He would later be greeted by the Original Universe's Gaster who prompts him to give up, explaining that the bright future he is chasing will lead him to failure. He dismisses the claim, unwilling to accept the consequences.

* While busy in the Doodle Sphere, Ink hears water droplets coming from the [=XTale=] universe and decides to reenter the universe, only to find out that the only inhabitants left is Cross and the spirit of X-Event!Chara. The two end up bonding together, albeit hiding the soul fragment of [=XGaster=] from Cross. X-Event!Chara took this as an opportunity to scout through the many alternate universes that Ink was showcasing.
* Later, Core!Frisk would try to invite Cross into their Omega Timeline, to which he refused because he still believed that his world could be saved. During their next meeting, Ink blatantly tells him that his world cannot be restored, which only worsen Cross' mental state.
* Not long before the events of UNDERVERSE 0.0, Error!Sans takes notice of Cross and runs off with his soul, much to Ink's disapproval. This causes Cross to be corrupted and only lingering on X-Event!Chara's determination, and this causes him to escape his empty universe.
* '''UNDERVERSE 0.0''': Sans wakes up in an empty void to where X-Event!Chara/Cross tells him what he is and requests that he stay in his universe. When Sans doesn't approve, he ends up taking half of his soul in order to stay within his universe, only to be intercepted by Ink, who manages to chain X-Event!Chara/Cross up with his paint ability. Requesting that they turn back his soul back to Sans, X-Event!Chara/Cross ends up escaping their grasp and returns to their universe out of desire to rebuild their own.

** As the two side clashes over each other, Nightmare witnesses the assets of Underfell's Snowdin being transferred away. Sans manages to keep Cross distracted while Cross' influence on Underfell!Sans is overwritten, and he ends up leaving as they obtained the core code of Underfell. While Underfell!Sans and Sans gloss over the loss of a portion of their universe, Ink is taken captive by Error.

** With the OVERWRITE button once more in use, X-Event!Chara does a "demostration" on Underswap!Sans, Underswap!Papyrus, and Underswap!Chara on the effects of the OVERWRITE button, which interests Nightmare on the topic of pain and suffering. In the midst of this, X-Event!Chara attempts to ask Ink to give him the vial that he was tasked to protecting, but [=XGaster=]'s hidden presence in the battle, of which he overwrites Underswap!Sans to take him down, stops him in his tracks, and he is forced into continuing to serve his portion of Nightmare's deal.

* While busy in the Doodle Sphere, Ink hears water droplets coming from the [=XTale=] universe and decides to reenter the universe, only to find out that the only inhabitants left is Cross and the spirit of X-Event!Chara. The two end up bonding together, albeit hiding the soul fragment of [=XGaster=] from Cross. X-Event!Chara took this as an opportunity to scout through the many altenate universes that Ink was showcasing.
* Later, Core!Frisk would try to invite Cross into their Omega Timeline, to which he refused because he still believed that his world could be saved. During their next meeting, Ink forces him to meet reality, which only worsen Cross' mental state.
* Not long before the events of UNDERVERSE 0.0, Error!Sans takes notice of Cross and runs off with his soul, much to Ink's disapproval. This frees X-Event!Chara from Cross's body, allowing him to escape from his empty universe.

* In desperation to continue saving dying universes, Ink ventures into an endangered universe to prevent this universe's Gaster from destroying all that he had created by showing him the multiverse. This Gaster feels motivation to continue to venture forward with his own universe, for his and their child's sake.

* '''TIMELINE VI''': Weak yet willing to fight his father, [=XChara=] tries his hardest to take down his father's anomalies, but being unable to kill them, he's immediately taken down and half of his determination is swapped out for [=XGaster=]'s perseverance, granting him the power of the OVERWRITE button and kickstarting the X-Event experiment.

** Later, the X-Event shows to [=XSans=] the original universe and how it differ to the current sitatuion at [=XTale=], explaining that if they don't kill him, they won't see a future where they can make mistakes and create more timelines, and where he'll be the one in control. [=XSans=] does not agree with the X-Event's motivates, prompting a fight against the two where the X-Event finishes him off with the OVERWRITE button. Feeling sorry that he ruined his dress, the X-Event clarifies that once this timeline is overwritten he'll nickname him Cross, and that he'll create something better than what [=XGaster=] has done.

** Unappeased that Cross is still unwilling to accept the X-Event's offer, [=XUndyne=] and [=XPapyrus=] end up beating Cross down, in light that he would interfere in their business to take down [=XGaster=]. Cross survives, and decides to take things into this own matters.

* While busy in the Doodle Sphere, Ink hears water droplets coming from the [=XTale=] universe and decides to reenter the universe, only to find out that the only inhabitants left is Cross and the spirit of X-Event!Chara. The two end up bonding together, ableit hiding the soul fragment of [=XGaster=] from Cross. X-Event!Chara took this as an opportunity to scout through the many altenate universes that Ink was showcasing.

** In the aftermath of 0.0, Sans agrees to hear more about Cross, and how [[SeamlessSpontaneousLie he was the lone survivor of what was a Genocide Run, without any RESET ability possible]]. After hearing his story, Sans opts not to join Ink in search of Cross, and desires to stay with his friends in his own universe.
** Cross agrees to X-Event!Chara's plan to rebuild their own universe, and absorbs Sans' soul fragment, allowing Cross contol over the body. Later, while discussing how to traverse the multiverse, Cross goes berserk over being unable to save his own universe, gaining the attention of both Nightmare!Sans and Dream!Sans, the former manages to obtain a deal for him to cause pain and suffering in exchange for traveling throughout the multiverse, and the latter warning Ink!Sans' about Cross and Nightmare's deal.

** As Sans enjoys a picnic with his friends, he begins feeling unwell, culuminating in Undyne hitting him hard with a volleyball. He soon realizes a subtle X over his soul, and he leaves and tries to call out to Ink. Frisk, who was chasing Sans, is concerned over the situation, and after realizing that half of his soul is missing, Frisk is reluctant to break their promise and RESET their timeline, to which Sans disagrees. Ink manages to hear Sans' plead and enters, to where he and Sans explain the whole issue to Frisk. Sans asks Frisk to hold him until he returns from getting his soul back, as he and Ink venture off to finding where Cross has been transported to.

** Feeling discontent with the failures Cross dealt in Underfell, X-Event!Chara tries to take over control over his body, which Cross puts an end to. After a minor skirmish between him and Nightmare, Cross is brought over to Underswap, and notes a distictive familiarity in this timeline's code and his own universe's code.

** The synopsis for this episode of Undernovela is that Frisk had been kidnapped while Asgoro and Sin were fighting over the latter's marriage of Toriel, forcing the both of them to team up in order to find their child. The kidnappers? Cross and X-Event!Chara. Immediately taken aback by their appearance, Error is stunned when Ink enters the universe itself and uses [=XGaster=]'s powers to overwrite Sin and Asgoro, eagerily happy that Error has joined in their game.

** Because of Error's disapproval of their game, [=XGaster=] entices Ink to lock him up in his own Anti-Void while taking back his other perserverance half from Cross's/X-Event!Chara's soul. X-Event!Chara plan of obtaining the other half of the OVERWRITE button were demolished, and he ends up dying without a soul in sight. [=XGaster=] then proceeds to wipe out Underswap!Sans and Underfell!Sans, returns Sans back to his own timeline, and feeling a bit sorry for [=XChara=], rejuvenates his soul and hopes that he uses his Determination on his behalf. Knowing that it would be harder for [=XGaster=] to persuade him to join, he brings back Cross and gives him the choice to join him or not, before evading and will be waiting for him.

* In fear that the X-Event and his creation would take him down for the consequences he has done to them, he asks Ink to carry half of his soul in a vial and stay far away until he begins his "third phase" of their game, explaining that he'll be able to handle himself with [=XChara=]'s determination.

-->'''[=XGaster=]''': "We will be waiting for you, Cross."

* '''TIMELINE IV''': Still hoping to stand up for Ink, [=XGaster=] attempts to begin a Genocide Route with [=XFrisk=], curious if his determination will ignore his order. His route is sabotage, as his assistant [=XTale!Alphys=] sneakily reveals info to [=XTale!Muffet=] about this timeline, which leads her into convincing [=XChara=] to rebel against [=XGaster=]. He does so by utilizing the first instance of the RESET button, angering [=XGaster=] on the premise that the RESET button will cause other timelines to coexist.