Tiaral

Otherwise, these Heckelian factions are all so suspicious, it's hard to tell who to side with.

We need to check each faction one by one, starting with the one that seems more "serious" historically.
I suggest the Sun, the Serpent, and the Red Hand.
The first are proud and unlikely to deceive us.
The second... they're better than the Mantis, with whom the Sun faction says "you can't do business." They probably didn't just appear out of nowhere.
The lazy ones as representatives of the third side will do. Probably better than the Mist, who might send their own Phantom in a mask instead of a scout./

Min, Stefan, and some kind of Terminator from Alcina,

/ Why Stefan? Because of the Nihonites?
My character, however, isn't too keen on the Nihonites, and he spent quite a bit of time in Naliar, but such a nasty operation would really be a letdown for her.
And Siv is right, it's dangerous. If many other characters seem more or less equal in strength, then here there's a feeling that the Naliar king is some kind of Saakashvili, attacking in a clearly losing position, hoping that someone strong will help him (but won't)./