Martha Liberty is The head of intelligence, sending out Loa, this suggests she is a Voodoo Priestess, which if you check the connection between Christianity and Voodoo, she may have a connection to the White God as solid as Father Forthill. As a wizard she may have access to soulfire like Harry (LTW was able recognise soulfire, this where he may have seen it).
Importantly LTW was the only Senior Council member to see Harry wield soulfire prior to BG, not all Senior Council members may be aware that he has that power up on top of everything else). I believe a WOJ indicates one of the Senior Council is a saint, Martha is the best candidate, and that is her hidden nature.
Eb has the Blackstaff, and we have seen more of it in operation than before. It is clearly Mother Winters walking stick, the outline he assumed of a cackling hag gives no doubt that this is his hidden nature.
LTW is basically an adopted Bigfoot, he apprenticed to River Shoulders making him fairly unique.
Christos was nothing more than a Stalking Horse to divert attention away from other members of the Senior Council.
Ancient Mai we know little about but probably Dragon connected.
The GateKeeper we have been shown what his hidden self is.
This leaves the Merlin. I think he isn’t just a bad guy, he is THE Bad Guy. Cowl. He manipulated La Fortier and Petrovich in relation to Harry as a child their deaths were to cover this. Petrovich’s death backfired, he wasn’t expecting Eb to take up a seat. To a certain extent La Fortier’s death backfired, Peabody was exposed and then was killed by Morgan following Harry’s investigation.
Basically there wasn’t two conspiracies to keep Harry occupied, there was one, Nemesis and the Merlin/Cowl working together. Nemesis did for Thomas and had Listen attack the Carpenters. Merlin/Cowl whistled in the Corner Hounds (he has a grudge against Eb, and this requires a mortal) and set up the political ploy against Harry for his expulsion.
The long term leader of the White Council is Cowl, Black Council member.