Toxic Metaplanes?, or just a subsection of the standard metaplanes? Options

[Semerkhet]

At some point in the next few sessions my team is going to embark on a metaplanar quest to permanently destroy a toxic free spirit. Well, the team magician is going anyway, accompanied by the metaplanar simulacrums of the other team members. The toxic free spirit is "of Man." The PC magician has a custom Tradition similar to the elven "Path of the Wheel" in that it sees spirits as manifestations of the fae.

So, where should I send him for the metaplanar quest? Is there a separate Toxic Metaplane of Man? If not, are sections of the (functionally infinite) regular Metaplane of Man corrupted by toxic magic? Since this particular Free Spirit is stealing Karma from victims in Jack the Ripper style ritual vivisections, should I use some other metaplane like Fear?

I was also thinking that it might be cool to incorporate the magician's tradition into the quest by having the metaplanar geography and trials take on a distinctly dark fae feel.

Anyway, just looking for ideas and input. Thanks much.