I am confused as to whether the listeners expected the Fused to return to Roshar when they summoned the Everstorm. They assassinated Gavilar in order to prevent the Fused from returning. As far as I understand it, they didn't want the Fused to come back and dominate their people. Could they have summoned the Everstorm in such a way that the Fused wouldn't have returned? Was summoning the Fused a way of acknowledging that they had no chance of winning the war against the humans without the help of the Fused?