Summer riots are a fact of life in the Cities of The Peninsula. It is hot and uncomfortable in The Cities during the summer. Every few years there will be too little food (or its prices would be too high), there will be too little water in the wells, there will be too little work, taxes will be harsher, or there will be some event that angers the common men. The young (and a few others) will take to the streets. The Loud Ones they are called. They will chant, they will break things (and the occasional fire), they will threaten, and occasionally in the worst cases, they will viciously attack people and property - especially those of the noble caste who they see as the cause of all their problems (or responsible for not doing anything about them).
The Loud Ones are one of the reasons the Nobles have summer homes.
The civic leaders will of course send the militia after any Loud Ones who riot outside the lower quarters. They do little except threaten. In some cases the Loud Ones go around them and still make a mess of better parts of the town. It is the rare riot that sees much blood. After the riots, it is traditional for the civic council or the noble lords to apologize and seemingly do something (or publicly try) to address The Loud One's concerns. The people accept this and calm down. It is the way of thing. Life continues on.
Yet the riots in The City seem to be happening more frequently these days. They are growing worse. They are growing more bloody.
Summer is coming. It is going to be very hot.
In the last few years, a few people have notice a dog that has been with The Loud Ones. That should not seem unusual. A city has always had its share of street dogs. This one has a distinctive reddish color (think Irish Setter). The Riot Dog seems to be bigger than most, with the more pointed traits of the imported dogs that Nobles are using to guard their compound (think German Shepherd). He also seems to be wearing a blue scarf tied about his neck. (The Scarves seem to be the item to wear when "being loud". They are also worn when attending civic/ political events. Blue is the city color). However this one seems to be "where the worst of it" happens.
In fact the local garrison commander has his men looking for during any unrest, as it is his "flag" for finding the trouble. He originally thought one of the owners was a Loud One ringleader. That is not the case. No one claims to own the dog, know its name, or where it normally lives.
Since the Riot Dog seems to have a Noble Guard Dog's blood in him, people will quip about even noble dogs will diddle with the common folks and abandon their young.
Some of the smarter Loud Ones have noticed The Riot Dog too. They have taken it as their mascot. Some of the Loud Ones have taken to calling themselves The Dogs.
In fact, they do know where it lives. The Dog, which they call Smart Dog, tends to live in The River Quarter where the wine shops and cafes are where the young and idle rich hang out. The University students and scholars often frequent the quarter. It is from the wine shops that the young firebrands and future civic leaders come.
The Dog is obviously more than a mere dog. There are several ways you can use The Riot dog.
1) He is a guardian spirit for the peoples of the city, ensuring that the riots don't get too out of hand. He will try to shepherd crowds away from scared militias. He will lead cooler and smarter leaders to places where they will do the most good. He will lead the militia on a merry chase if he can. He is also hanging about the wine shops to influence the young leaders. He might even bring PCs into the area because he thinks they might be useful when the times come. (Hey, this dog.. I think it likes me. You want me to follow you boy?)
2) He is the form some demi-deity or demon that feeds off the chaos. The Dog will continue to be "where the action is" to absorb the chaos, the pain, and energy. The Creature absorbs energy and uses it to influence things.. making people do things they will regret. Eventually the city will be in flames (or close enough) and it will have enough energy to manifest its true form (or its master's true form) upon the world... bringing untold suffering into the world. Of course the PCs will want to stop this. So they need to find the Dog and keep it from the chaos. They then need to find some way to banish it.
3) He is a creature that causes the chaos, the avatar form of some chaos demon or god. This takes number two to a new extreme. Where the dog is unrest seems to happen. (Strange, there was no reason for that..) So as the dog seems to sleep near cafe's and wine shops where young firebrands get started about the price of food and the taxes from the nobles. They get the idea to do things "violently". Well you see how this goes. Find the Dog and then stop it. (Of course, it will have some other form that will be dangerous that it will change into when cornered).