Gideon Ninth/Locked Tomb: Ancient history

The actual plot is really really cool but impossible to understand at first. I got sucked into trying to summarise the most important or cool points as they happened rather than as they were told in obscure hints and flashbacks. Part one of um several.

( Massive spoilers for everything )

I tried to stick with what was fairly clearly implied but I've probably remembered a few points completely wrongly, do check me on anything which doesn't sound right.