If you are doing arrow of extraction quest and have gotten to the part in the main quest were mythic dawn assassins attack you becarefull if you run into the smithy(forgot is name but i belive it has smithy in and he is wearing a brown apron)He turns into a mythic dawn agent and attacks but if u fight back and kill him you will have to pay the bloodfine for killing someone other than the arch mage. This also can be used to your advantage though if you run to the guards while he is attacking THEY will kill him and you will be able to take the castle key off him (perfect for those with low security)
Also i would like to add even though the gray fox says you can kill the arch mage if you are a member of the mages guild you will get kicked out of the mages guild if you kill him