Backstory?

[Strazio Rockwell]

Are there any rules on retconning backstory of a character before their introduction to the Omniverse? I'm assuming you can't change anything that'll make major changes with their current continuity, but can one change details of their backstory as long as they don't majorly overhaul anything?

I wrote my alt's backstory back in 2015 and I feel like it needs to be polished and less weeb-tastic

[Handsome Jack]

Anything Pre-Omnivrrse can be changed freely. Within reason.

[Ezrihel]

Every time I've seen this asked the ruling on it has pretty much been: Yes, but you cannot change at what point in time they were taken from their universe and summoned by Omni.