This is post 6 out of 25 in the Cygnus Series of a September of Short Adventures.
This is another one that's not so much a single linear "adventure," but instead more like an ongoing situation that can develop in many different ways, depending on the DM's interests and the players' actions.
The short intro: A family of of rakshasas has taken over the big gambling hall in a town. They quietly killed and replaced some of the employees, but they keep the original owner (Norris the Tall) alive but under psychic control, to handle the business. They originally planned to have a huge feast of all the customers of this popular establishment, but that would have closed the place down and they'd be on the run again. They learned that it's best to keep the place running and profitable, since that ensures a steady stream of patrons... a fraction of whom come in down on their luck and alone, who won't be missed once they lose their money....
About the rakshasas: Although many of us have loving, nostalgic feelings for the stereotypical image of Tony the Tiger in Hef's robe, I'm thinking more of the traditional Indian folklore that gives us guys like these...
As stated above, the rakshasas are discriminating regarding the patrons that they choose to haul away and devour. They've learned to ask nonchalant questions to figure out which solitary patrons wouldn't be missed if they disappeared.
In an extended campaign, the gambling hall itself can serve as a setting for PC carousing for many sessions before the players start to figure things out. RPG PCs tend to travel in groups and not be too mopey, so to the rakshasas they're merely fodder for money via the rigged games. I haven't worked out any detail for the layout of the place itself, but I found a wonderfully detailed RPG gambling hall online called the Gold Goblin. (Two floors above-ground, and two below -- all laid out and keyed. Very nice!)
The games themselves? Ah, you know about Appendix F of the 1st edition AD&D Dungeon Master's Guide, right? See also some other cool ideas by Michael Curtis. There were also some simple dice games in the Church of the Big Gamble from the old module L1, The Secret of Bone Hill. I've also been fascinated with Terry Pratchett's idea of a cursed 7-sided die, which nonetheless appears cubical to the unwitting rube who uses it. For those who may not be looking to simulate the actual gambling, have a look at my more abstract idea for contests of skill.
DMs looking to start off this setting with a more specific "adventure hook" can have the PCs be approached by a distraught family who is looking for their missing breadwinner. The dude was drunk and depressed one night when he went into the gambling hall, and blathered on about how nobody really cares about him, how nobody will miss him when he's gone, and so on. This was music to the rakshasas' ears! But it turns out his family did miss him, and they want to hire the PCs to investigate what happened to him. Other NPCs can provide clues about where he wandered that night, which will point them to the gambling hall.
(The genesis for this idea was the first ever episode of The Wild Wild West, "Night of the Inferno," guest-starring Victor Buono [Batman's King Tut!] disguised as the servant of a decoy villain.)