How can a disabled character fight (unarmed/sword/knife)? He only has one good hand, and the other arm ends at a stump at the wrist. Is a wristblade possible on the stump? Can he punch as normal (boxing skills)? Holds? The setting is fantasy, and military stuff isn’t needed at all.
Well, it’s been a couple years since we’ve talked about Götz von Berlichingen, so let’s remedy that.
Götz von Berlichingen was a German soldier in the early 16th century. During his career he served as a mercenary, Imperial knight, and even became a poet later in life.
Götz is significant, because in 1504, his right hand was blown off during the siege of Landshut. The full story was a messy succession war between the Bavarian duchies of Munich and Landshut. Having lost his hand, Götz had a simple prosthetic commissioned, and continued campaigning for 40 years. For context, he was in his mid-20s when he lost his hand, and continued fighting into his mid-60s. He would later go on to have a more advanced prosthetic crafted, which could be manipulated to allow him to hold objects. Most famously, this included a pen, which allowed him to write with his prosthetic. This is somewhat fortunate, as he left an autobiography, which forms much of the historical record we have regarding him.
Finding the autobiography (and even the play Goethe wrote) is fairly easy in the original German, though English translations are a bit harder to come by. (Translations of the play are a little more accessible, but Goethe took some significant liberties with history.)
While Götz is the most famous example, his use of a prosthetic hand was not unique in the era. The technology needed for these prosthetics were basic clockwork systems, and a similar level of mechanical sophistication to wheel lock firearms.
Since you’re working with a fantasy setting, it’s possible your world might have more functional prosthetics, potentially with more specialized applications. (Though, obviously, more delicate tools built into a prosthetic would make it less useful in combat. For example: If you have lockpicking tools built into the fingertips, you probably wouldn’t want to risk damaging them by punching someone.)
I’m not aware of any historical prosthetics that had weapons built into them. Wearable weapons are uncommon, but have existed at various points in time. It’s not impossible that your fantasy gauntlet could have a retractable blade built in. However, if the blade is damaged, the user would need to go through an entire process dismantling their arm and replacing the weapon, instead of just switching to another one.
Worth noting, it’s can be harder to break free of a hold, by someone who is missing a hand (and especially if they’re missing part of their forearm.) The easiest way out, usually involves manipulating the attacker’s fingers, and if they don’t have any, pulling their arm off will be more difficult.
Can you punch without a hand? No. It’s possible you could punch with a prosthetic (though, again, if it has mechanically delicate internal components, this may be a bad idea, depending on how it was designed.)
So, the historical answer was, prosthetics. This may be more true in your setting than in the real world.