Everyone I've played Elder Signs with has greatly enjoyed it. Many of them expressed interest in Arkham Horror when I explained its similar premise.There is only one thing I'm concerned about: the occult content.
Personally, I'm open minded about things with occult content. I've read the Harry Potter series, as well of a few Lovecraft stories with no problem. However, most members of my group are Christians that may be offended if the occult content is a prevailing theme. So here are some questions for Arkham Horror players:
I haven't played Elder Signs, personally, but considering both games are made by FFG and both set in the Lovecraft mythos, I would be surprised if the thematic content of the two were different enough to cause problems here. In fact, considering how well known FFG is for recycling content across games, you'll probably see some familiar artwork in AH.
As an aside, have you known these Christian friends of yours to be offended by the likes of Harry Potter? I mean no offense, I'm just wondering if this concern is based on past experiences or if you're just assuming that a bunch of Christians will be offended by occult stuff. I used to hang out at the local Campaign for Christ office when I was in university (me being a practicing agnostic, btw) and I never had any problems raising various fantasy subjects with the people who worked/hung out there, that's all I'm saying. Just because they have a vested interest in Christianity doesn't mean they'll flip out over vaguely pagan mysticism in a board game, unless of course you've seen them do so in the past…
As I said before, the fact that they've received Elder Signs well is a good indication, to me, that they'll likely be fine with AH, too.
-What is the extent of the occult content in this game (if any)?
It is present, but not really overwhelming. Aside from dusty grimoires and spells to cast, most of the mythology is sufficiently alien that it doesn't really bear resemblence to any particular religion, IMHO.
-Are you required to partake in anything (besides spells) that may be considered offensive? What comes to mind are things like joining forces with the opposing side or anything that implies worshiping or sacrificing to the Old Ones. If I can explain that we are against the occult elements, I might have an easier time getting this to the table.
There are probably a couple of sacrificial events floating around (I can't think of any in particular), but mechanically speaking the currencies used to pay for such things are defeated monster or gate tokens. So if you're sacrificing anything, it's dead monster bodies. =P
Some of the Outer World encounters (in particular) might involve descriptions that sound like worshipping other deities to some people, although I would personally characterize them as simple exploration of a VERY strange environment. Maybe paying lip service to the Outer Gods, at worst.
There is one investigator character from one of the expansions (Innsmouth, I think?) who is an ex-cultist. If you're really worried about offending your Christian friends, you might remove that one from the deck, or at least ask them if anyone has a problem playing an ex-cultist character.
-Are the event cards gruesome enough to be offensive?
I wouldn't describe any of the event cards as gruesome. Violence occasionally happens, but rarely is there even a description of blood spilled, let alone anything more offensive.
-Are there certain expansions with content that I should avoid?
If they're fine with the base game, I can't imagine any of the expansions would cross the line.
I know these questions seem obnoxious and irrelevant (they are to me). It's just that my friends will probably be sensitive to anything demonic or satanic in nature. Thanks in advance for any insight!
It's good of you to show concern for the feelings and beliefs of your friends. If you have any serious doubts, my best advice would be to ask them about it. This doesn't necessarily mean showing the game components from Arkham Horror and asking if they mind this or that. Just open a conversation about what sorts of things they would consider inappropriate in a board game. Try to define some specific lines they are unwilling to cross, and then we could probably give you a much better answer about whether or not this game would offend them.