Excuse the unspecific question title. Hard to ask this without putting spoilers.
In D&D 5e Tales of the Yawning Portal, there is an updated version of the legendary Tomb of Horrors. At page 225, the PCs enter room 30, called:
False Treasure Room
The description goes like this:
The room is lined with lead and has antimagic properties, so no spells will work within the room, and no magical properties of items of any sort will properly function except those that detect an aura of magic or a place of desecration.
So far so good. In the room there is...
A bronze urn that, if opened gently, reveals an efreeti that "will grant three wishes for the party and then depart".
So, what happens then? The book give no additional insights on this.
Obviously the PCs have a good chance to anger the efreeti and not get the wishes at all, but it seemed weird to me at first that Acererak would put something that can, in some circumstances, help the party. I ran the adventure in an Adventurer's League this past week and I pondered on this when I reached that point. The PCs decided to trust the efreeti and ask for some reasonable wishes (I suspect some meta on their part, but that's beside the point).
What I did...
I remembered the properties of the room they were in. I interpreted the "grant three wishes" to literally mean "cast the spell Wish" and I roleplayed the efreeti attempting the spell 3 times, failing to, and then leaving, utterly frustrated. It seemed to go along with all the cruel jokes played by Acererak and how nothing is truly helpful in this dungeon.
My issue with this:
Both the room properties and the efreeti's description are short, apart from each others (not even on the same page), and do not reference each others. If what I did was the actual intended behavior, I feel that it was really obfuscated and rely on the DM doing quite a bit of logical thinking. I certainly wouldn't blame another DM to have miss it and grant 3 wishes. And what would have been expected if the PCs had taken the urn outside the room (and the antimagic field) before opening it?
All in all the players and I were satisfied with how it played out at our table, but we were left confused about what was the intended scenario.