Ceradis

In WoR epilogue, Hoid mentions to Jasnah that Tanavast had bought him drinks before. The letter also talks about the vessels with what seems to be personal familiarity so this makes sense and kinda confirms that Hoid personally new most if not all of the shatterers.

So iirc many of the Diagramists pursue their own goals within the diagram itself. There is a part of the Diagram that says Mr. T will either have to make an ally of Dalinar or end up assassinating him. I think that Graves' original goal was to get Elokhar out of the way fast enough for that to happen but it ended up taking too long. If I can find the quote that made me think that I'll post it here. Edit: here is the quote I was talking about. We’re allowed to pursue our own interests and goals until we’re called up.” He shook his head. “I thought for sure my interpretation was correct, that if we removed Elhokar, Dalinar would become our ally in what is to come. . . . Well, it appears I was wrong.

So I do recall this WoB; however, it seems quite clear that the author of Ars Arcanum is not talking about fabrials here. Her discription of these abilities as esoteric and her later discussion of fabrials make it unlikely that this is what she's referring to. Once again, though, she could be wrong

I noticed that in the Ars Arcanum for WoR Khriss says that her "research suggests that, indeed, there should should be another series of abilities that is even more esoteric then Voidbinding." Then continues to say she thinks it's unlikely that it's the Old Magic. Does anyone have any ideas as to what this could be? It's important to note that as an in-univers source the Ars Arcanum shouldn't be taken as completely true so she could just be wrong but that explanation doesn't seem like a very satisfying one.