The Nexus is a fusion of the eight fallen humans.Frisk and the others were a random anomaly of nature, with their only sole purpose being to help free the monsters. Now that their mission was accomplished, Frisk's determination is forcing them against their will to recollect the other souls to form "The Nexus".
- The Nexus isn't malicious or a threat to resetting the timeline. But rather it's trying to perform a reset on itself in order to erase its existence as a protocol to protect the monster's future. Kind of like restarting a game back on it's latest save point to get rid of a glitch.
- The Nexus is kinda like a robot that follows Asimov's laws... but instead of humans, it's monsters. So essentially, it won't fight back. Which can make a bit of a boring battle... So while the Nexus begins gathering enough determination to make this reset, the beginning portion of this fight would more or less consist of many obstacles that the monsters have to dodge in correlation to the Nexus following the third law, until they can get through to Frisk's conscience (like Frisk did when they were all in Asriel's body).
- The Nexus tries perform a reset on itself in order to erase its existence as a protocol to protect the monster's future.
- Obviously the gang doesn't want to lose Frisk. So they begin to do everything they can to save them, even if it means battling the Nexus.
- You'd be the monsters fighting against the Nexus in control of Frisk's body and the other human souls, including Chara. The current idea behind it is that this battle plays a little similar to Earthbound, where you control one character at a time to tackle certain events within the fight.
- This battle revolves around a loose theory that Frisk, Chara and the six other human souls are all fragments of one singular being/soul/conscious/etc.