From caldera, take the road to Gnaar Mok. You will meet a redguard trader (Pemenie) which will ask you to escort her to Gnaar Mok. Do that and you will receive the boots of blinding speed, which improve your speed by 200 but have an unpleasant side effect which can be countered by night eye or magic resistance.

i never bothered to get those boots, i odn't know whay