Pick up the quest in Fractured Plain at (13457, 3112) from Miltiadea Charus.
White balls outline the borders of the race course. If you try to take a shortcut or stray too far from the intended path, Ashen Assassins will appear and "correct" your actions.
You receive a temporary skill, Sprint, that uses the Endurance boost to make you faster!
The race course ends at Keldum Revan, the turn-in NPC, near the Splintered Shallows Travelstone.