It used to be in RoC, but they removed it
. In some maps, you can however pick up a Staff of Silence to help you fight casters. But its a rare item that I have only seen appear in Sunrock Cove on the island creeps.
Be warned bout faeries, they can be webbed into fiend attack range. However, they have 12 bonus armor doing this so try to get a rejuev on them so they aren't slain fast.