Writing a story where an emissary from a more advanced civilization has arrived to give weapons to a a civilization that has only recently graduated to crossbows so that they can defeat their enemies. I'm just not sure what the technology IS. Should I go with the obvious and have it be gunpowder/firearms? Something a little more techy that these people will still be able to figure out, repair and perhaps replicate? Or just go with something that's essentially magic? I don't know anything about my advanced civilization yet so the possibilities are pretty wide open.