Everyone hates on the undead until they need some cannon fodder. 

Going to be honest, I wouldn't be surprised if Tushienia actually knew that this great Darkness was coming (What with being necromancers and all, same wavelengths) and even attempted to unite some nations against it... but failed because no one will listen to them. 

As for religion... Tushienia doesn't exactly have one. The goblins highly revere nature while the liches promote the idea that godhood was merely a matter of power and the key to ascending was to discover a path to achieve that power for yourself. Transcending the limits of the mortal coil by becoming a lich was merely a means of extending the time one had to figure out the secrets of becoming a greater being, but it is not the only path to greatness. 

The Holy Novgorod Imperium is going to hate our guts for it, but whatever. The Great Darkness from the east is going to claim them first anyway... and we will take in whatever refugees wish to flee in our direction.