I wonder if Yda will make the mistake of siding with the Ala Mhigan Resistance. We know Ilberd isn't a particularly pleasant or sane person and will no doubt engage in yet more horrific acts in the name of his misguided cause. It also seems like he's...interested in reclaiming Ala Mhigo so that he can be in a position of power.

I'm assuming that it is indeed Ilberd. It seems likely - there's many signs that point to it and he's a great way for the story to move towards having the Warrior of Light see Garlemald in a more sympathetic light if he starts killing Garleans indiscriminately.