The Raid Mirror

From the introduction: Halad al Bim didn't take all of his relics to Tannoch with him when he died, and now a pack of blight orcs has found his cache. At the cost of many lives, they have cracked the secret of al Bim's mirror, a device which not only allows viewing of distant places, but travel as well. Now, blight orc raiding parties are appearing a hundred leagues from the blight, raiding the unfortified villages beyond the borderlands. They slaughter everyone, take everything, and leave no tracks. They've eaten their way through three valleys' worth of cattle without a defeat. That sort of thing can make a baron lose sleep.