Chris

Mary was pretty well explained. The core, that originally attacked people and jack fuses with Mary. Nobody knew until later. There was a scene where Jack and Mary were talking after those people got blown up where you see the l-core touch her.

Sepentia I didn't feel like it needed more. Maybe a little, but the AI was behind the scenes causing chaos to depopulate humanity to make it easier to manage.

I do wish we got more in regards to L-zone though.