Hello, tavern! I have a DMing advice question for you!
A while ago, my players came across a magic item (a spear) that has some specific properties when it interacts with a particular named monster (a campaign villain).
However, they never actually bothered to identify the item (they don’t have any wizards/similar, so they didn’t even try). But they used some inference and deduction to know that it could be used against the villain.
I remember one of the players suggesting that maybe the spear did X, which was untrue. But this was speculation; they knew that they didn’t know its actual properties. I think the plan was to talk to a wizardly ally when they got the chance.
But they never followed up, and over time they’ve all decided that the spear does X when actually it does Y. I’ve tried to remind them that they never got it actually identified but they always conveniently forget that I told them that.
Last session, they heard a story about some magical legendary spear that did Y and their response was like “oh, that sounds like our spear except it must be another version because ours does X, not Y.” So they are now, apparently, 100% certain that the spear does X even though they have no reason to be so certain.
Part of the issue is that its usage is limited – only against the campaign villain, and they’re not quite there yet, but they’re planning for the ultimate showdown, in which this spear will come into play.
What they think it does is summons the villain (if you plunge it into the ground or something like that) but what it actually does is immobilizes the villain (if you stick him with it). So as you can see, the actual usage is quite different. They are planning around using the spear to summon the villain when that would have no effect.
My question for you, oh Dungeon World Tavern, is what should I do about the spear? What would you do? Should I let their plan work? Should I let their plan fail? Should I have a wizard tell them what the spear does?