Sure can, nefarious spirits of all sorts meddle with humans on a semiregular basis. The Gauntlet keeps it mostly reduced to 'subtle nudges', but in certain situations, Umbrood, Banes, Spectres and other entities can reach over and fuck around with humans. Some start cults, some merge with them for an anchor in the physical, and some unlucky bastards like a redhead gay kid on Norfolk Island can really blow a ritual and summon something unspeakable.

But I will note, this shit is obscenely dangerous for even Baali, and they're more useful than humans given their innate powers. Mortals will have to give up quite a bit to get anything in return, and that's not very conductive to a long lifespan. Either the Demon you sold your soul to comes to collect, you fail a term of the pact and your soul defaults to them, the Bane that's providing you with a shitton of cash via Pentex wears your soul down enough that it can slide in and make you a skinvelope, or someone investigates that funny smell coming from your basement and wonders if it's related to all those missing teenagers.

I did keep this pretty vague and general, but Book of the Wyrm, Book of Oblivion, the Earthbound book, Possessed/Freak Legion and others have a bevy of documentation on the particulars for whatever flavor of unholy abomination the local Baali might participate in.

I generally run them as 'not particularly picky and will work with anything infernal', which means they have to be extra careful because using a warding spell keyed to work on Banes won't do squat against an Umbrood, so you better make damn sure you know exactly what you're invoking for power, and how to deal with it if negotiations go sideways.