MTG Salvation

I'm making a Chainer, Dementia Master EDH deck and I was looking at the card when I thought that I could use the last ability as a board wipe to essentially keep my commander safe. Basically are there any cards that will allow me to change my opponent's creatures into nightmares? Thanks!

Yes, there are. But they're blue - stuff like Unnatural Selection and Imagecrafter. Unfortunately, Chainer doesn't get a lot of options here.

Are there any Donate-type cards in black or colorless? You could give your opponents a Nightmare Conspiracy.

Avarice Totem perhaps? Leave it to you to figure the rest out...

I'm fairly positive donating a Conspiracy is the only option for changing opponents' creature types in mono-black. And Avarice Totem or Gauntlets of Chaos are the only way to donate an arbitrary permanent in mono-black. (Although for Gauntlets of Chaos, you would have to first turn Conspiracy into an artifact/creature/land with something like Liquimetal Coating.)