When I mentioned the idea of a Jewish D&D campaign, mezzsing commented:

Messzing commented: “… I see no reason why you could not have an Jewish version of D&D. It seems odd, in fact, that no one has already tried it. Resting on the Sabbath is a great idea for weary soldiers of fortune and if you had priests in your party, perhaps they could gain experience points towards casting spells, if they were studying in addition to resting. Or is that too irreligious?”

I think the deep question is how the DM would reward or penalize Jewish adventurers for observing, or not observing, halacha (traditional Jewish law). There are lots of possibilities, depending on one’s view of the religion, and you could only hope the adventurers would at least understand what the DM was up to. For example:
· The DM establishes a “guilt index” for each player, and their likely degree of guilt about their observance would affect NPC interactions.
· The DM gives simple rewards for acting halachically correctly, such as being invited to NPC meals, being given scholarly books, etc.
· If the DM believes that children are less likely to get sick when your mezzuzzoth are kosher, the adventurers’ level of observance could have spectacular side effects.
· How would NPC’s respond to your refusal to eat certain food?
· The DM could quantify Tumah (ritual impurity) and have it affect the game.
· Let’s not ignore wonder-working rabbis. For whom would they work wonders?
· Bat Kols, anyone?
· The sky’s the limit if you want to assume each adventurer has a certain level of kabalistic competence.

Perhaps this sort of thing has not been tried because no two Jews could agree on the right way to do it. Once upon a time two Jews were stranded on a jungle island. When they were rescued, the rescuers noticed that there were three menacing deep pits with signs of fresh digging. They asked one of the Jews what the first pit was.
“That leads down to a horrible dungeon,” he replied. “I’ve done some adventuring there, it’s terrifying but the rewards are great!”
The asked the second Jew about the second pit.
“That pit leads to an invisible tower,” he replied, “I’ve done some adventuring there, it’s terrifying but the rewards are even greater!”
“What about that third pit?” they asked.
The two Jews responded at once, “Oh, we would NEVER adventure into that dungeon!”