Running is an ego found only on boots and the lightning scales unrandart which reduces your movement delay by 10% (rounded up). This stacks with other speed enhancers, such as the Swiftness and Haste spells, and has the advantage of requiring no maintenance to keep active. It is widely considered to be the best boots ego available.
Bear in mind that suddenly moving faster may drastically change your combat tactics. Chasing down fleeing enemies and escaping pursuers, especially those without ranged attacks, will suddenly be much easier. Characters with permanent allies should learn Recall or change their travel speed with the CTRL-E command, because most of them will be left behind while exploring.
Note that the bonus is not a flat decrease of 0.1 to movement speed; it is rather a 10% decrease. This means that it reduces movement speed by 0.2 for barachim (and nagas in the case of the lightning scales), and giving barachim the normal movement speed of 1.0. This is not symmetrical to the ponderousness ego, which is a flat increase of 0.1.