The Ashlands pack lives in a cave at the base of Sarn Gebir (Northwest of the Eastfold)
Years before the summons from the white wizard to join the ranks of Isengard, they raided outland villages at will.
As they became a growing threat, Eomer made it a personal mission to wipe them out entirely.
He nearly succeeded when a royal decree( from Gríma Wormtongue ) disallowed he or his men to travel that far from Edoras. Alowing those who escape the chance to regroup in a safe haven.
Of course He would ignor the order when ever he could and his men would gladdly follow.