Did Vikings ever worship their traditional Gods' enemies, such as Surtr, Jörmungandr, and Fenrir?

by Granfallegiance

I've been thinking about the ways that some religions portray their End Of Days myths as great battles with distinct sides. In a world where some exposed to Christianity choose to worship Satan, this makes me wonder if similar practices arise in other religions where some might choose to worship their traditional Gods' enemies directly.

Were there worshippers of the deities and beings that opposed Odin, Thor, and Heimdall at Ragnarok? What form did their worship take?

y_sengaku