What I don't know is: Nidhogg started the Dragonsong War after Thordan killed Ratatoskr. ¿But why he didn't started it when the Allagans killed his brother Bahamut and kidnapped his sister Tiamat? ¿And why he didn't declare war against the Garleans as well after his father Midgardsormr "died" at the destruction of the Agrius?