Diabolism

In the vast multiverse of realities that exist ouside of Noma-Lum are certain beings, collectively known as Elteri, who can be compelled to manifest in our world and act at the behest of a master who has completed the proper rituals (often as part of the summoning spell). While the term "diabolism" (and the professional designation of Diabolist), is sometimes used to refer to any interaction with the Elteri, it's generally understood to refer specifically to dealings with the malicious variety of Elteri collectively known as "demons."
Intentionally summoning or entering into agreements with the Elteri is widely held to be a foolish act that never ends well for the recipient of the Elteri's attention, but for most people this belief is inverseley proportional to the believer's means of engaging in such behaviour. When actually presented with a chance to avail themselves to an Elteri's services, people are extremely adept at constructing justifications for why this particular situation is different form all the others. History and folklore are full of stories about people who were double-crossed or tricked by the Elteri despite certainty that they'd found a way to outsmart or ward themselves against these beings.
People are considerably more judgemental when it comes to trafficking with demons, especially on a regular basis. Most Elteri are potentially more dangerous to the person dealing with them than to others, but demons are inherently malicious and difficult to control, so every demon who manifests in our world is a potential threat to the whole community. While there are no laws against diabolism--Mage Law would make such a thing nearly imposssible to enforce--most people consider the practice contemptible. As a result, most diabolists keep their activities a closely-guarded secret. The handful of people who openly admit to dealing with demons tend to be those who have made something of a profession of being scandalous. In many cases, their reputation far outweighs their actual experience.