User blog comment:SayuriDarling/The Sword of Summer Official Discussion/@comment-24055022-20151020030254/@comment-24883778-20151021200936

I can see where are you going with this - the theme of a weapon + one of Loki's children. Sumarbrander and Fenris, Mjolnir and Jormungand... going by that theory, it's logical that the last book's weapon should be somehow connected to Hel. And looking at her pet dog is a pretty clever idea...

However, nowhere in the Tyrfing Cycle - the collection of legends about the sword, it is never stated that this blade belonged to the god Tyr.