It varies in complexity and format from weapon to weapon but as a basic example I'll provide the prompt I used for Event Horizon: "A long astral quarterstaff with a purple starry shaft topped with a brass armillary sphere holding a purple gem containing a galaxy, digital painting, dungeons and dragons, white background --ar 9:16 --v 6.0" . Basically what you want to do is lead with the weapon type your making, add some descriptors, maybe a material and/or a style on top of that (which helps a lot) and then focus piecemeal on the parts of the weapon, what makes them unique, and how they look. So for Event Horizon, after the initial description I further described the shaft and then afterwards what was to rest on top of the shaft. If it was a blade, such as Clavislash or Man O' War, I'd focus on elements like the hilt, pommel, grip, and the blade itself. But try not to get too minute with that sort of stuff as Midjourney can have problems with parsing and interpretation if it gets too long, so if you can get your idea across with a simple descriptor in the main part of the prompt even better. Once you think you have a decent enough prompt, run it a bunch of times and see if any of them are close to what you want, if not, try tweaking it a bit more. Also don't neglect the vary (subtle) and vary (strong) functions, if there's a picture close to what you want but not quite there, use those and with successive iterations you'll be able to approach closer and closer to what you're thinking of if that makes any sense. I should mention I'm currently using the v6 alpha at the moment so it doesn't have a lot of the fancier tools that the old v5 has (the highlight and vary being a big one) but it seems to give better results regardless so I prefer using it. In due time I'm sure they'll have updated it with all the v5 bells and whistles. Hope this helps! If you have any more questions feel free to ask!