speed feat here:
"Around me on the swirling dunes, a cohort of Ra’Horak fights, Solari warriors far from the temples of Mount Targon. They have marched with fifty spears, three weeks into the desert—a distance I have crossed in moments—to investigate a power that grows, even as their own wanes."
assuming 9 hours down time(eating, sleep, shitting idk) leaves 15 hours of marching time.
60*60*15*7*3 =1134000s
human walking speed = 1.4m/s : https://en.wikipedia.org/wiki/Walking#Difference_from_running
1.4 * 1134000 = 1587600m
using 3 and 5 seconds for "moments".
1587600/5 = 317520m/s
or about mach 925 MHS.
1587600/3 = 529200m/s
or about mach 1542 MHS+
Low end = mach 925 MHS
High end = mach 1542 MHS+