Grimlings are a wizard's attempt to circumvent social engagements by creating a cadre of servile creatures that are equally as dissocial and self-sufficient.

Being cats, they do most - if not all - the things that cats do, but not particularly remarkably well, because Nymus foisted upon them a sense of self and an intelligence that is not present in cats in nature. Therefore they are conceited and they are so willingly. While fearless, they delude themselves of their own grandeur in order to be such. And yet for all this intelligence and merit, they will never do a damned thing you ask them to.

The only reason they exist is because Nymus would need to speak to real people in their absence. They are dutiful and clearly intended for a purpose, but I cannot help but feel that a wizard should do better than to become introverted and surround himself with cats. Nymus for whatever reason rushed headlong into 'widowed and lives alone'.