The snake could be Midgardsormen, or Jörmungandr as I think it's called on wikipedia, that coils itself around the world.
When the final battle between good and evil comes this worm is supposed to get killed, and mortally wound, the thunder making god Thor.
The worm also got two siblings, one is the god of the underworld called Hel, and the other is a giant wolf called Fenrir.