These are MY theory's. I could not find it anywhere on the internet. Please do not plagiarize this. Anyways, let's begin. I strongly believe that the line "Six of us went down into the pit, only one crawled out." Is NOT a reference to the number of guardians needed in a raid fire team, but is instead referencing the children of Oryx. (Crota and The four swarm prices) You're probably wondering who the 6th entity is, but it's clear isn't it. Eris, the one and only swarm princess! (Every thing past this is mostly out there) I believe that Eris, being the only swarm princess, was up in line to become a hive queen after Crota's original death. Another theory is that after she took 5 guardians to feed to the hive, she realized her evilness, and fled to the tower for refuge. Another theory is that her father was Oryx, and her mother was... Well any human or awoken, as those are the only races she looks like. Maybe she was ostracized for being a "Mutt". That would explain her leaving from the Hellmouth. I know most of these theories are probably wrong, but I just had to share them. I'm fine to answer any questions in the comments.