This is the real clue that Saturnyne left me. It's the tournament key. A... casting circle. As Champions retrieve their swords, they return here to a position within the circle. When each of these symbols is touching its corresponding sword at the same time, then this opens our tournament portal. 
The Voltus Glade is a casting circle used to open the portal for Saturnyne's tournament between Krakoa and Arakko.[1]
History
After the death of Rockslide in Otherworld and his failed resurrection, Polaris constructed a casting circle in the Voltus Glade with the stones that were Rockslide's body.[1] Following the pattern put into her mind by Saturnyne,[2] the casting circle would act as a portal to take Krakoa's Champions to Saturnyne's tournament between Krakoa and Arakko.[1]