Dresden is a fallible narrator. While I don't think that Jim set up the Dresdenverse to be a huge exploration of this artistic device (not like the movie Barry Lyndon or something like that), Jim has mentioned the problem of the fallible narrator in streams, interviews and WoJs.
In the aftermath of Battleground and Peace Talks, I've been questioning my assumptions about Christos. We are very much led to assume the worst of Christos by Harry:
*Christos strong-armed his way onto the Senior Council in the wake of LaFortier's murder. Threatening the Merlin with succession of his non-Western faction.
*Christos is disliked by McCoy for being "unpleasant," and the circumstances make McCoy and Dresden suspect that Christos is Black Council.
*In his first "action" as a Senior Council member that we see, he flips out on Dresden as he is treating with Arianna in an attempt to end the Red War. This, of course, reinforces our perception of Christos.
But, is this really fair?
First, with Peabody in his position, why would the Black Council actually need anyone on the Senior Council? Peabody was controlling the Council fairly effectively without actually needing a vote. He already had access to all the information that the Black Council could have needed.
The Black Council goal appears to have been broadly to set factions of the Council against each other. Would it be better to put a Black Council traitor on the Senior Council or a powerful and effective member of a disgruntled faction on the Senior Council?
Second, the fact that McCoy doesn't like Christos is hardly evidence of anything. McCoy doesn't like anyone much IMHO and "unpleasant" is quite the stone for McCoy's glass house. McCoy and Dresden are brawlers. Neither are going to be inclined to like politicos, even though to be fair Christos is legit as a combatant.
Third, he is an arrogant and pompous blowhard over impressed with his own diplomatic skills. See Wizard, Senior. The incident with Arianna ... well, Dresden was half-insane and out of line as everyone but Dresden saw. Lucio, Molly, Ramirez and even the Merlin tried to calm him down.
Fourth, as detailed in another thread. I find it suspicious that Christos was sent to Chicago while neither Merlin nor Mai attended the talks. Sure, Mai is not handy in a fight. But Liberty doesn't seem to be either. While Christos and LTW and McCoy are good in a scrap, so is Merlin. In short, Merlin sent everyone who might support Dresden into the fire (except Rashid who had other things to do) and kept his supporters and Dresden's sure opponents safe in Scotland behind the wards.