I'm just going to put this out there, but I think Nidhogg has some ties to the Monetarist plot. The reason is because of the timing of the wyvern skirmish, as well as that loose end from Dreams of Ice when it turned out the Ivy was also dealing with the Harriers and Monetarists.

Remember when Teledji went in to accuse the Scions of regicide, and there were Templars with him as he entered the banquet hall? Aymeric noted something was off about that, and there was Teledji's smug grin as he looked at him before leaving. I bring this up because of what "Templars" did at the Gates of Judgement earlier.