From Paradigm Concepts Arcanis campaign the
City of Secrets: Nishanpur might fit (There's an adventure too
Blood reign of Nishanpur). Substitute the Demons with the Dream Dark, Cultists with the Inspired and you should be good to go. Though I do not know much about the quality of these products.
Paradigm stuff is generally pretty decent. In fact, Nishanpur was an off-shoot of their Living campaign which was (in the early days at least) reckoned to be one of the best developed of the living format campaigns, with a very well developed plot and setting. Not sure how you'd get your hands on them, but as well as Blood Reign, there are 2 (?) years worth of the Living arc plot adventures which must add up to about another dozen or so 'rounds' worth of material. Maybe asking nicely on the Living Arcanis yahoo group (as livingarcanis.com has disappeared - maybe in preparation for the launch of their new system?). If you do try and find any of that stuff, there is a bit of work to do in that one of the pecularities of the setting is that the only metal armour and weapons allowed in the city are made of special 'sacred' steel; and it is very expensive. You can try to smuggle other stuff in, but if you get caught... Might add an interesting twist to the game at least!
When I first saw this, I had a momentary pang of nostalgia - a combination of chalking up another year on Saturday, and the untimely death of Ronnie James Dio on Sunday. Firstly I remembered the original Thieves' World box, spending months adventuring in Sanctuary, meeting the likes of Jubal, Lythande and Enas Yorl.
Then I thought of Irillian, home of Zotoquaan the wizard, which appeared originally in White Dwarf. It had that slightly wacky, slightly amateurish feel of a lot of early WD, but done with the very best of intentions, and hiding the odd gem, often in the least expected places

It was collected together in Best of WD Scenarios vol III, but a bit of web searching suggests that's about as hard to come by as Umbar unfortunately.
I've still got a very moth-eaten copy, which I did enjoy flicking through again for old times' sake. But in the end, it just made me feel old *sniff*