Swamped

1: They have done almost no damage, except to Rider, who I have no historical knowledge of personally but seems to not give a damn right now. The arrows or bolts or whatever seem to not even make it all the way through one wall of the wagon, so either they've got weak crossbows or you have a heck of a wagon. Could just... find something to give Rider cover and just keep going? But they'll probably just follow because they...

2: Probably REALLY want this stone or whatever it is, because they were fairly quick to stop shooting and draw up a message when they realized you were threatening to break it. Does that mean they can be trusted? Probably not. Can rider climb back into the wagon proper, and can you barricade the exits so they can't barge their way in? If so, could TRY talking to them. Still seems pretty bad.

3: In the end, this is a lose-lose situation. Unless someone here has a crossbow, then you could try to carefully retrieve the bolts and fire them back. Alternatively, hope they run out of ammo.

4: What's stopping you from just CHUCKING THE ROCK like they want? Pubert is in a bad deal anyways, it seems. Unless there is something immediately unusual about the lodestone, you should just chuck it. If they keep firing after that, then it's time to work out plan B.