Well, I have no idea what the lyrics say, but I'm guessing it has something to do with nordic mythology.
Níðhöggr (aglicized as Nidhogg), is a dragon that eats the roots of Yggdrasill. And Jörmungandr (Jormundgand on the lyrics) is the arch-enemy of Thor. They end up killing each other during the Ragnarök.
Text from booklet:
"The world of ice in the distant north is a very mysterious place. Among its fog and inside its ice, the seed of life is buried. When the heat of Muspel turn the ice of Nifel into a stream of water, the creation begins to take place. Even though the frozen water of Nifel conceal a spark of life, this is first of all a place of death and the world fear the lethal strength of the icegiants who were born here in the beginning of time."