Ahh the classic basement o’ rats. What do tavern owners keep down here that is so enticing to rats. Stored food? Booze? Maybe they should start reinforcing the walls. Inevitably the party will come across a basement full of rats or that will lead to a rat infested adventure. My thinking is why does it need to be that simple? Perhaps the rats are just your standard vermin those are great for low level starting adventures. Perhaps they are lycanthropic were-rats and the raids on the basement stores only happen during certain phases of the moon or season. Maybe there is a Wizard or sorcerer or even one employed by a thieves guild using these seemingly simple pests as a tool to gain wealth or overwhelm their enemies. A simple basement and simple enemies does not have to be boring and can lead int a great adventure.
Reality-Break 