[quote=Imperfectionist]The idea of the Sha'ir (a sorcerer who uses a small familiar as an envoy to the Outer Planes) works fine in D&D, considering that jinn in that game are natives of the those Planes and all, but how would it work without the defined Planes to travel to? The best I could come up with was that the Sha'ir sends the gen to make arrangements with various higher jinn, who then travel to her location and assist her with their power. Would she trade favors with them, or perhaps wealth? It's an interesting thought: what does a jinni ?
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Well, we could go based on the concept of King Solomon who had the ability to bind Djinni. Perhaps the Sha'ir has done something similar but instead of binding Djinni into items like lamps and rings, he or she uses a smaller Djinni familiar to send to the far distant greater Djinni for the spells. Why they do this? Perhaps a Sha'ir summons the full on Djinni into circles and uses the implication that they could be bound into an item as a threat to coerce their compliance.

This also would mean that there are some Sha'ir out there that routinely entrap Djinni into items. These might have to deal with Djinni reprisals. Certain Djinni might deal with these "nicer" Sha'ir, trading favours in return for them taking down their tyrannical brethren.

The other question is, pre-Islamic, why do the Djinni simply make humanity extinct? They certainly have the ability. Maybe the gods dwelling in the Kaaba forbid this or maybe Bahamut, the great fish upon which the world resides, starts thrashing when the spirits threaten to wipe out humanity?