This was originally one of our Labyrinth Lord supplements. It was featured in the fourth issue of the OSR magazine Brave the Labyrinth, which you can check out here.
The Magic of Chaos is a small supplement featuring twenty spells for monster shamans who are aligned with Chaos. It's Pay-What-You-Want, so check it out here.
If you want more info on our version of Chaos in the land of Cairnvarthi, check out our Labyrinth Lord supplement "Adventures in Karak," available here. Or you can wait until "Into the Arcaskdry," which will be the follow-up campaign to "Adventures in Rollingvale," which isn't even out yet. Then again, the Karak book is focused on Mithgarthr, which is in a different part of Cairnvarthi than Rollingvale will be. Plus isn't not written with Fifth Edition in mind. So I guess maybe wait? Now I'm rambling...
So anyway, yeah. Go check out The Magic of Chaos.