Sette is Tirna
She mentions a twin brother, and she is basically Tirna made flesh :P
I suspect the four gods are just some kind of magical programmers that made a game world they wanted to live in. And used the Khert as a save/load mechanism. It's possible it got out of hand and that the game is crashing hard rn.
That would make Lady Il the rogue AI and Ssael some NPC that realized that Khert was just a game.