Drops from Tomb-raiders all around Evendim.
(heard this is true)
You can also kill mobs to raise Warden's of Annuminas Rep.
All around Annuminas and Book 10 areas, elites giving 10-20 rep.
"A sash representing the allegiance of a Tomb Raider in Evendim.
Faction: Wardens of Annuminas (30 points)
Use this item to immediately gain reputation in this faction."
This item is also a random drop from the:
Steel-bound Lootbox (30-39)