Your players have run afoul of the city guards, but when you pull up the stat block you realize it isn’t going to be as effective as you hoped.
We present to you, the veteran knight.
To be regarded a veteran, most knights have seen their fair share of war and atrocity. Outside of a wartime environment, many veteran knights become watch commanders or household trainers who teach younger members of the house in warfare and force of arms.
Find this stat block, and others like it, in Houses and Heraldry for 5e on DriveThruRPG.
Houses and Heraldry
This book sketches out ten noble houses for your campaign. Each house is laid out on one page; the top half contains the house name, its motto, a representation of their heraldic device as it would appear on a shield, and an information block detailing important personages, numbers of troops, and vassal houses. The lower portion provides enough detail about the interesting characters of the house to get your imagination going, but leaves plenty of room for you to add your own details. See a sample here.