About the characters:
You already know most of the characters very well, but here are a few notes about some of them:
Six and Ledin are from Kwaide. They were both born no-names, so they have a lot in common. Kwaidians are literally thick-headed, because they have a very thick bone structure in their skulls, and the rest of their bodies which makes them very hardy. They can also be very intelligent, though you wouldn't think it, especially when two or more Kwaidians get together.
Grace is Sellite. The Sells were originally a corporation from Cesis which became so powerful that it decided to move its whole staff to an independent planet. This was Valhai, which they leased from the other planets in the system. Eventually they forgot their origins and became a new species, with extreme dedication to become ever richer and ever more powerful. They were, until recently, genetically engineered by decree, though Grace wasn't, since she was conceived on Xiantha. Grace is quiet but intensely loyal to her friends. She is scared of a lot of things, but that doesn't usually hold her back.
Diva is Coriolan. Not only that, she is an Elder's daughter, and was brought up in complete luxury. It has taken her much soul-searching and time to fight her way free of the prejudice that has caused to be ingrained inside her. But now she is free, finally, to enjoy a relationship which would have been unthinkable only a few years ago.
Both Bennel and Tallen are Coriolan. Bennel is a Coriolan bodyguard. This is a prestigious job on Coriolis and involves defending one of the meritocrats with your life. In exchange, your family is fed and housed, although no salary as such is paid.
Tallen is a member of the Namuri people, who live in the marshland near Mesteta. They do not agree with the meritocratic way of life, under which they are not allowed to earn, to buy, to sell or to trade. The philosophy of his clan is one of passive disagreement: they steal from the meritocrats, but do not take up arms against them. Tallen is not in agreement with this ideology; he would prefer to fight. He hates the meritocrats, especially since one of them, Tartalus, has started to kill members of his own clan, for 'fun', to 'cull' them.