I swear decoy, and rot go hand in hand with undeath. Though, it technically also goes with darkness. 

Have you considered a realm of an Abyss of eternal winter like hell? With ice and frost? 

Maybe even an ocean plane filled with horrors of the deep? 

Might keep things varied, up to you of course. I'm just throwing stuff out there. Anything could be given a paint of evil with the right amount of imagination.