My level 5 party is currently tasked with defending a small town from a raiding orc party. It is the first battle in a large war between this kingdom and the invading orc hordes. The half-orc paladin PC is on a mission to prevent the war so this is a very important event in the context of the story.
As such I put a lot of effort into setting up this fight. I have multiple types of orcs, a fully fleshed out town map and NPC stats for multiple locals. The party has recruited the townsfolk to help in their defense. The locals will mostly be using the commoner or expert NPC classes, with a couple of warriors for the locals the party had spare weapons for.
The leader of this town is a human retired war veteran with links to other important NPCs. His backstory is that he fought in multiple wars before getting a portcullis dropped on his leg, breaking it in multiple places. Faced with selling everything he owned to afford clerical healing or retiring he chose the latter. He is now the only military minded NPC in town.
When I started creating stats for this NPC I wanted him to be important. So, I followed my normal strategy of giving him PC class levels, 4 levels of fighter. I then added 2 levels of expert to represent his growth after retirement.
I have described him as a strong man of early middle ages. He wears chainmail and walks with a heavy limb. He carries a longsword and uses a cane with his off hand.
I want to represent the injury that caused him to retire in a mechanical way. Hopefully in a way that it will be obvious to the players during the fight. My only ideas were to reduce his movement speed to 20ft and giving him some penalty to dexterity. I was hoping for something better than that. I want him to still be a capable fighter but clearly limited by his damaged leg.
How can I create stats for an NPC to show their permanent injury?
If there is an existing mechanical way to do this, that would be the best answer. I would also accept any experience-based answer either from NPCs or PCs.