Yep. You've got the Thorne mages to thank for your presence here. The rest copied the ritual the Thorneans used.

[At least, from what Hector can tell. He's not sat in on any of the Free Cities' summonings to compare to his own arrival.]

You could say that. We're the only ones who can reach the Singularity, so each country wants agents they can send there to see their agendas done and their enemies' thwarted.