The plot point about Nidhogg and the six maiden is solved in Sword Oratoria, but Bell is involved.so i can only imagine that bell will somehow confront nidhogg because this is too important an enemy for him not to be involved. will the rest of this story take place in the main manga/anime or will bell somehow get sidelined in an event revolving around gods that he and hestia are personally connected to. i just don't see how they can do anything moving forward without him who is still the de facto mc even within this spinoff.
This part of the story is now at the start of the 12th LN of SO and this story arc is finished at the end of the volume.