- Kill Agnis.
Agnis is located inside the keep of Fort Greymoor which is west of Whiterun. The fort is initially garrisoned by bandits, however if you have started the civil war quest line (by joining either the Stormcloak Rebellion or the Imperial Legion) it is garrisoned by soldiers of whichever faction controls Whiterun. If the fort is garrisoned by hostile forces, it is possible to sneak in or to just kill all the enemies. If your faction has control of the fort, the assassination is much easier. Either way, Agnis is easily found inside the keep and, having only a dagger and some modest clothing for protection, is equally easy to kill. After the kill, report back to Nazir for some levelled gold as a reward.