My player are not faring well against the Pulex they encountered two weeks ago. Time to send in the rescue squad. Time to introduce the Harpers.
In my campaign, the Harpers aren't all-purpose good guys, but an order specifically charged with making sure no-one ever becomes king. Mittel hasn't had a monarch since the days of the Vampire Kings (most of whom were only metaphorically bloodsuckers). Eventually everyone got sick of having to overthrow tyrants, and the Harpers were formed. They are funded by all the landed nobles, who pay up because not paying means maybe you think you should be king, and then everyone gangs up on you, lead by the Harpers.
Anyway, these NPCs are going to show up and get the PC bacon out of the Pulex fire. They're some scruffy, backwoods Harpers.