ok so here's the lowdown:
First Fusion/Singularity - once upon a time Genesis and Bereave were fused as one entity. This entity held both creation magic (orange magic) and destruction magic (white magic). This is the Big Bang, Singularity, whatever creation myth you want to ascribe to. They could create and destroy at their will but were incredibly unstable and lonely. Eventually they ripped themselves apart into....
Genesis - for lack of a better term, Genesis is the "half" of the first fusion that wanted to split off. They stole 95% of the creation magic and then started to try to make things. They are very poor at making things.
Bereave - the other half, that didn't want to split. Got left with maybe 5% of the creation magic and all the destruction magic. Extremely upset about this; at first tried to convince Genesis to re-fuse. When that failed, accepted their position and started killing off the things Genesis was making.
Magnitude Fragments were formed during this time. They are the most powerful of Fragments, since they are basically tiny little chunks of the first fusion that gained sentience and spread out across the worlds Genesis was making. There's only a few in existence; one is being held captive in the Alpha Timeline, the others are ??? idk we'll find out
Genesis' Worlds are what we call the Timelines. Each one was vastly unstable and violent, so Genesis abandoned them in their infancy to try making a new one with a slightly different formula. There's pretty much infinite ones now for various reasons, but they also served as a sort of bread-crumb trail so Bereave could follow Genesis and pissed-off-ly taunt them about the fact that their worlds sucked and hey let's fuse again. Genesis continues to ignore the pissbaby and be a pissbaby of their own flavor.
Eventually Genesis creates a stable timeline. So stable, in fact, that it doesn't instantly start warping out of control or getting fucked up. So stable, in fact, that its mere existence stabilizes all of the existing timelines so they stop like imploding in on themselves. Genesis is so shocked by this that they split into three more Gladar, further breaking apart the first fusion's magic. This timeline is the Main Timeline and where 99.9% of story talks place. Basically all of this talk is a backdrop for the main storyline, because the timeline stuff is only relevant in small circumstances and is mostly flavor text because help I think about this too much
From Genesis' splitting not only comes the Big Three, but also regular Fragments - miniscule chunks of magic that were lost in the explosion and have some semblance of timeline powers. Fragments will be discussed later in more detail just stick around
Bereave finds the Big Three, who have named themselves Petrichor (nature), Alphanumeric (technology), and Marvin (time). Petrichor and Alphanumeric make the Starter Gladar - the original Gladar of each major Gladic Group. This includes:
Time Gladar: Nonstop, Continuum, Beginning, Restless, Neverend
Space Gladar: Gladwin/Virgil (same person at the time), Perihelion, Aphelion, Synodic
Color Gladar: Black/White (who then proceed to make Red, Yellow, Orange, Green, Blue, Indigo, and Violet)
Elemental Gladar were made by Marvin all at once at a later date, and Wanderers have varied modes of creation. Assume that if a Wanderer's backstory isn't explained in their bio, they were made by Alpha/Petri.
Alphanumeric and Petrichor instantly begin squabbling about what to do with their creations. Alpha feels that the Big Three should take charge of the timeline and rule as leaders/gods, to ensure nobody is hurt/damaged. Petrichor thinks they should fuck off and let the Gladar do whatever they want and let them make mistakes on their own. Marvin pleads with them to stop fighting, but they both bail. Marvin takes off, being the only one with the timeline-viewing powers Genesis had, and decides to dedicate himself to making sure the other Timelines are ok out of guilt from Genesis treating them like trash.
Time passes. The Main Timeline (MT) basically oozes excessive amounts of Magninium, both because there's now a ton of beings in it, and also all those beings are making Universes that are just producing more magic. This at first means that the Main Timeline creates a bunch of Connected Timelines, which all sprout from the main timeline & follow its general path. Connected Timelines can have major event shifts (i.e. maybe like, idk Nonstop gets killed during a war or something) but are directly based off the Main Timeline's foundation. These are usually designated with a number and then letter - for example, the K-1 Timeline is a Connected Timeline, but the Alpha Timeline is not.
Time passes. The MT is still producing an obscenely excessive amount of Magninium, which now means that there's too much and it doesn't know where to go. The Magninium starts eating other Timelines, slowly. Marvin has an "oh, shit" moment and makes the Elementals, who are all decay Gladar (save for Magninium, who is a generator Gladar) to eat up large amounts of excess Magninium. He also then dedicates himself more closely to stabilizing the other timelines.
A LOT of time passes. Eventually Bereave is tired of moping around, feels like Genesis has greatly wronged him, and splits himself into three. These are the Inverse Three, and consist of pure opposites to the Big Three (Alpha, Petri, Marv). They are, respectively: Cosmos (space), Terrene (earth), and Kismet (fate). The Inverse Three & Big Three instantly start squabbling and/or fighting among each other. Collectively the Inverse Three & Big Three are referred to as the Big Six. This splitting also creates more Fragments.
Note: Marvin & Kismet are aware of and can see the other Timelines; they exist in all Timelines simultaneously. It would be like playing infinite video games at once; you simply can't concentrate enough on all of them at once, but you *are* in control of yourself in all of them. Petrichor, Alphanumeric, Cosmos, and Terrene are not aware/cannot naturally see other Timelines, but they are always generated alongside the Marvin/Kismet of each timeline, like NPCs that join you at the start of the game. They have no idea you're playing infinite other video games where they are also NPCs, but if you explain it to them nicely they'll try to protect your in-game avatar so you don't get killed while you play the other games. I hope this analogy makes sense.
Genesis and Bereave existed in a similar fashion to Marvin & Kismet, but slightly altered: There was only 1 Genesis and they could be in any Timeline they wanted, but could not, say, exist in two at once (so Genesis can play video game 1, but if they want to play video game 2, they would have to stop playing 1 and physically move to 2). If they re-fuse in the Main Timeline, the same thing occurs: Marvin/Kismet no longer see/experience the other Timelines all at once and the other Big Six in other Timelines also fuse. If they re-fuse in any other Timeline, Connected or Not, this does not occur - that Genesis/Bereave is temporally locked to the specific Timeline they were created in.
This can get messy - if a locked G/B is formed in an alternate Timeline, and then a G/B then fuses in the Main Timeline and then unfuses, the locked G/B will also unfuse at the same time as the main G/B. So it can be confusing for alternate-Timeline G/B and usually the Marvin/Kismet of that timeline will have to explain to the others why the fuck that just happened.
Also if a locked G/B is formed, Marvin/Kismet can no longer access that Timeline for the duration of that fusion's existence, since they're part of G/B and the components aren't aware when they're in a fusion like that. This can be helpful since it takes stress off Marvin to tend to that specific Timeline, but can also be bad if the Petri/Alpha of that timeline are malicious. It's a coin toss, basically. (This does not apply to normal Gladic fusion rules; please see the Gladar page for info on how normal Gladar fuse). Wow that probably made no sense and was very confusing I'm sorry this is so bloated alksdngldaskng
Also actual storyline was happening during all that section between Genesis & Bereave splitting. Genesis splitting is basically the start of the main timeline and Bereave splitting is *literally* several hundred quadrillion (yes, quadrillion) years in the future from that. I can't accurately tell you how long that took in a scope that you would understand, but basically it was roughly (very roughly) 5,286,343.61233 times the age of planet Earth (4.54 billion years). Also Numbers years are in general longer (403 days vs. our 365 days) so yeah basically it was a period of time literally incomprehensible to humans, so don't worry about fully trying to understand how long that period of time was.
And most of this has nothing to do with most stories - in fact, most characters aren't aware of the Timelines, let alone the big Six, let alone Genesis/Bereave, let alone Fragments. It's just a big backdrop to everything going on.