So, I had a closer look at the soldiers and their logos.
The Niflheim soldiers and the soldiers behind the grumpy man have the same weapons. The guns have a red circular logo on them. They have the same face armor. They also have a similar silver cross logo on their chest armor.
See this image of Niflheim soldiers below. We can confirm they are from Niflheim because of the red Niflheim logo on their armor.
Now, the soldiers behind the grumpy man are carrying the same type of weapon, with that red circular logo (a little hard to spot, but you can see a little red there).
The similar silver cross logo.
The only difference between these soldiers is that the ones behind the grumpy man don't have the red Niflheim logo on their armour. Perhaps these are just a higher/lower class variety soldiers from the Niflheim army?
If this is true, then that would mean the grumpy man is also from Niflheim.
While I am at it, the hooded man also has a white dragon logo visible, which is similar to the Niflheim logo.
His henchman also has a logo (golden cross) that is similar to the silver cross mentioned above. Perhaps the hooded guy is also from Niflheim.
Thoughts?