If we knew that answer, our life here might be a great deal more purposeful. They don't seem inclined to answer us on their motivations, or how they choose who comes here. I don't know if they do, or they just claim to.

[ Istredd is suspicious because in his mind, it would make the most sense for them only to Summon people who will be helpful to their goals and that they can control. Why bring people to Thorne who won't trust them or play along, or would fight back if forced into anything? It is irrational so he doesn't trust it. He thinks it might not be many steps away from them opening up a dimensional hole and plucking someone from it. ]

I do wonder how much Thorne knows about the original Summonings. There probably were notes about it from the High Mage who started it, so perhaps the knowledge we were connected to the Singularity is what inspired Ambrose to try the same.

[ This is all speculation though. Ambrose won't answer questions not even from the Summoned he's come to a pleasant relationship with. They're still just objects to him, as far as Istredd can tell, baubles that he brings her for his own motivations. ]

They believe the Singularity is waning, weakening. They may think we can fix it. But it may be we're making it worse.