In the Peace, The King himself identifies to the conspiracy as the Grey Lord, takes the conspiracy over and runs it to his own ends. This one (of the many) personna of the king ceases to exist at the deposition and does not reappear in any of the later books. As to who the king becomes after that.... Suffice it to say that there are a few dim hints, but he's in the stories quite regularly. Two of the main characters will eventually figure him out, but he's been practicing his deceptions for an extraordinarily long time, so it won't be easy.
In The Friends and The General, the former Sean Reilly, now Donal XII, is at least twice called the Grey Lord. Others have a tendancy to term him this because he is characteristically morose, cyclically depressed, slightly cynical, dresses colourlessly when not in his state robes, and keeps himself out of the media as much as possible. People who are introduced to him for the first time in his role of behind the scenes manipulator do not usually recognize who he is at once, thus the moniker "Grey Lord". In this, he is (partly wittingly) taking lessons from the king's example. I allow the reader to travel along in the headspace of characters such as Tad for a while until they realize who he is.
The Dark Lord is Thomas Monde, but without revealing a spoiler, there is more to his conspiracy than one man, quite apart from the fact that he is manipulating some of the MacCarthys. Monde is not acting entirely alone IOW. This will be hinted at in "The Nexus" and become more obvious in "The Builder" and/or "The Throne". Who his real partner(s) is/are....
Just one error in your summary: Malone arranges the incident with Mara at the games. Thomas is definitely NOT happy with him for doing so. Indeed, BYAM, he considered killing Malone for that. You see, he has a certain, shall we say, paternal interest in Mara. Also in Catherine, but that's for later.
Rick Sutcliffe, Administrator Arjay Forums