Through a series of odd rolls, my party managed to get themselves stranded on Maladomini. They ended up making a surprisingly solid contract with a devil, 5 days of their service in exchange for protection, and they closed off a lot of the obvious loopholes. The only one I've found that they forgot is - no prohibition against ordering them to kill good creatures.
One of the PCs is an Inquisitor of Osiris, so my rough plan is to send them to Set's realm to attack a minor temple complex there. Why the devil they're working for has a grief against Set's clergy, eh, some slight from centuries ago or other. The order will be "Kill every being in the temple," or something to that effect, and they'll find a couple good prisoners while they're there. There's the fun moral dilemma bit for them.
The only issue is that I'm afraid of it becoming too much of a standard dungeon crawl, which doesn't feel quite right, especially considering they're only 5th level. A few straightforward combats won't hurt, but I don't want them to be 90% of the session. I'm thinking about having the temple have a false entrance, pyramid-style, with some traps and things to lure them off the main trail and go with Hell's general theme of deception. Other than that, I'd love to hear any ideas for how to throw in some puzzles or other sorts of things than simply hack-and-slash. Thanks.
Traditionally, Set was a god of deserts and storms (among other things) so you could include some sandstorms and other mav-vs.-elements situations just in order for the players to get to the temple complex (and this is if Set isn't angry or aware of their arrival).
Since the party is around 5th level, you probably don't want Set involved directly; but here are a few ideas off the top of my head:
-As this is Baator where people are always trying to claw their way up the power structure, perhaps the PCs are discovered by a head priest at a smaller, neighboring rival temple and he provides additional information to infiltrate the main temple. Perchance, this rival priest or his lackeys find the PCs moments before they were about to die in a desert sandstorms (furthering a sense of "debt")
-Perhaps the main temple the PCs are asked to take out is protected by a minor artifact of Set. So before the PCs, the rival temple (or the devil's forces) can strike, this item need to be removed/destroyed/corrupted (e.g. perhaps some Osiris or Horus related blessing acts as a "curse" to the evil item). So before they engage in a lot of combat, they have to covertly raid
-If you want to use the idea of the deceptive crypt you mentioned, perhaps the supposed protecting artifact (or the means to destroy/disable it) is located in a burried crypt. But when the PCs get there, they find that it was a big trap set up by the head priest of the main temple trying to draw out those who would try to usurp him. This could be a huge puzzle/death trap (with a lot of puzzles related to Egyptian mythology)
-Perhaps the forces of the temple are too great for the PCs to take on directly. Perhaps it would be in their best interest to expose the rival priest and cause the two sects of Set to go at each others' throats. Perhaps the PCs could lie about disabling the minor artifact (or maybe they expose that it never really existed) to get the rival temple fired up to attack and to dishearten the defenders of the main temple.