aco175
Legend
You have a good plot with the rats to take the PCs from levels 1-5 when they encounter the rat king and save the outer city. They can find out another p[lot near the end of this to lead they to either the orc problem, the noble demon problem, or the dwarf umber hulk problem. This may take the PCs to level 10 when they save the whole city from that. You gave them a choice on what path they wanted to take and along the next path you can drop hints about the other problems they did not take. Maybe the nobles are now plotting against the PCs if they are becoming heroes in the city and dealing with the orcs after the rats. Maybe the giants join the orcs if the PCs are dealing with the nobles. Develop the longer plot based on the PCs actions.
Another thing you want to develop are NPCs. Maybe the PCs stay out in the villages and farms. The farmers will ask the PCs to deal with the problem through the local innkeeper. There should also be other adventuring groups trying to deal with the problem, but having a hard time. Team up with a group to deal with a sewer den of rats and a mid-level boss, then have the group contract the disease to maybe fight the PCs later. Eventually, everyone cheers the PCs for solving the problem.
Another thing you want to develop are NPCs. Maybe the PCs stay out in the villages and farms. The farmers will ask the PCs to deal with the problem through the local innkeeper. There should also be other adventuring groups trying to deal with the problem, but having a hard time. Team up with a group to deal with a sewer den of rats and a mid-level boss, then have the group contract the disease to maybe fight the PCs later. Eventually, everyone cheers the PCs for solving the problem.