Yes it's based in Westgate, but it's also pretty much only concerned with Westgate and eventually ruling the city (and the small matter of raising of a kingdom of vampires). There are no PC rulers of Westgate, which does leave me wondering what exactly player members of this organisation would do - other than strut around Westgate.
I still think the Shadow Thieves are the better option. They're based in Amn yes, but they have guild houses all over. Plus, they have the advantage of a long-standing animosity with Waterdeep (their former base of operations), upon which they wish to avenge themselves.
I do understand the desire to move evil roleplay away from the Keep – which is Cyric's city in essence – but rather than spreading the already small evil playerbase more thinly, I think other options could be considered. In later years Cyric even begins to accept that other gods really are gods, which would probably lead to less religious persecution and, in general, less ass-hatery from Cyricists
I'm not sure where you were going with the diabolic evil comment though – the Zhentarim, for example, will engage in legal operations if it can and the Shadow Thieves are no worse than the Night Masks. Besides, I'm not sure there's much more diabolically evil than wanting to build a kingdom of undead
Just my two-copper.




