User blog comment:Jopjopjop/Volume 19 Spoilers/@comment-68.53.63.249-20141130210927/@comment-16281343-20141130222434

I was just about to confirm it.

~Yeah, Nidhogg is the only remaining one that has yet to appear / mentioned that was revived. And it makes sense since
 * Vali → Odin → Norse myth → Nidhogg.