Really?
Because I'd have thought the Crawling Chaos would've much preferred a virgin maiden - You know how hard it is to find one of those these days? If it's rarer, it's more valuable, and I'm sure you don't want to invoke a mask of Nyarlathotep without a decent sacrifice - Peeving off the servitor of the outer gods is probably not a smart move.
And besides, we've only just finished the temple - If the great one smites it now the brotherhood will have wasted like, their whole Summer or something. Maybe we could like, I dunno, raid a convent and steal a couple of nuns. This particular mask is the one with the thing for nuns, right?