Difficulty 1 out of 10 - Seek & Destroy:

The Guide in the Newcomers' Hall has been bothered by an
unusually large black rat! Search around for where the
rodent is getting in, kill the offender and give the
corpse to the Guide as proof. Make sure you kill the right
rat, and beware: there may be more than just rats lurking
about, so tread warily...