The JVLN Lance Cannon, the first model of which is known as the "Hand Lance of the Prince", constructed for M-Xalbriss, is a musket-like firearm. Sporting a durable barrel bound several times with extensions in places to allow for the smooth travel of harpoons, the weapon is designed to rest on the shoulder of the wielder for stability, with cushions designed for comfort and to reduce recoil. The firing mechanism is a hatch with a ring attached, and on the other side is a portallic blade. By closing the latch, the locking mechanism activates, sealing the hatch shut until the button is pressed to release the lock and allow the hatch to be pulled back. The entry of the perfect edge into the gunpowder supply will result in the combustion of the gunpowder supply within the casing, launching the harpoon forwards with impressive speed, as well as a concussive burst that will likely have substantial effect on close targets. The actual ammunition is a steel harpoon, inside of a casing packed with large quantities of gunpowder, with the gunpowder storage having increased capacity due to the casing connecting to an extradimensional storage space, which is also ignited upon firing the harpoon for added oomph. The casing containing the gunpowder and harpoon is "enchanted" to be able to use magic fuel, the normal affair such as knowledge plasma, aetus, or perhaps even distilled violence, to construct new supplies of gunpowder and harpoons. Energy can be infused into the casing while still in the musket with the external conductor bands, though filling the extradimensional stash will cost extra energy, so the portal leading to it may be toggled on or off by rubbing the casing, though this does require the casing to be removed and prevents rapid fire. As well, there is a non-magical ammunition model, though many testers have preferred the regenerate casing as several other Crush-Tech products are capable of synthesizing useable fuel, somewhat negating drawbacks of requiring a power supply. Non-magical ammunitions also come with portallic blades on the end of the harpoon for slightly enhanced penetration power, though portals have to be manually applied to magically generated harpoons. In short, it's a gunpowder based harpoon megamusket that works exactly like how someone would expect it to work except when someone feeds it magic juice, which causes it to do magic things like regenerate bullets.
@Klabss for candleworld. @M-Xalbriss for the request for a gun.