The Ashton Concordance
The Ashton Concordance is a magical agreement that states that no Skizziks and Lorcatha could have any kind of alliance. Doing so could potentially do harm to or destroy the multiverse.  Widow Groat revealed that Shemeshka was actually the mediator that helped to draft the concordance. Her payment for helping to craft the agreement was that she got to keep a piece of Diath's ancient soul.