After some further discussion, Endian's Deminsional Anchor prevents any sort of teleportation, summoning, or portals from working within the boundaries of her area. Fortunately for you, her area, while quite large, doesn't compass the entirely of Grafdakka as he fuses and builds with Balrog. Getting to his head should be easy enough with his new size, though getting to Endian herself would require you getting there by foot.

Basically it's mostly being used to protect herself, rather then Grafdakka. Not that he really needs the protection.