So, Estinein. Drops his guard for 'but a moment,' then suddenly Niddhog takes over in a fashion that would make CATS proud. A touching moment, but one big problem -

It made no damn sense.

Consider the context - one eye had just been drained, twice - once to overpower the barrier of Azys Lla, and another to kill a ascian (which is even REMARKED UPON RIGHT THERE), and the other had just been sapped to transform the Archbishop and the Heavens' Ward (albiet, after consuming Lahabrea). So, unless Lahabrea was some sort of uberconduit the likes of which the world has never seen, how the hell did the eyes, in their drained state, manage to overpower the dragoon in the mere less-than-a-minute he was holding the things?

This gets even stupider in light of the fact that King Thordan's son held the bloody things for who knows how long (easily upwards of ten minutes at the least), both at once, and he never so much as saw a hint of going super nidhogg sayian - and this was when Nidhogg's eyes were at full power - immediately after getting ripped out of the wyrm's sockets. Plus Nidhogg wasn't even dead at the time!

I like the story overall but this is kind of a glaring diabolus ex machina.