[quote=@Raijinslayer]
[@Joshua Tamashii][@Joshua Tamashii]Nidhogg isn't a mortal soul, but an Immortal spirit. He could do the same as Phelegthon and take a true form, but it would take too long while he could spend his time enjoying his freedom, which is much more important to him.
[/quote]

So he's a deity. Pray tell, what does he have domain over? Though I suppose the obvious answer domain over the dead. Was he worshipped at one point? Why was he sealed in the body of a dead dragon? Why was he sealed to begin with? If he values his freedom so much, does he view it as worth his time to bring form the ire of other deities, other beings with power as great as, or greater, then his own?