Swamp Raider is a medium armor set. The 5-piece set bonus now adds 400 Weapon Damage to your Poison and Disease Damage abilities.
This makes Swamp Raider very similar to other sets that add Weapon or Spell Damage to specific damage types and abilities, such as War Maiden, Netch's Touch and others. This update has made Swamp Raider a very useful set for Stamina-based builds that use a lot of Poison and/or Disease damage.
Swamp Raider is part of the base game and drops in Shadowfen in the Overland content. You can also find it on Guild Traders. Each set item is bound on equip. You can acquire medium armor, jewelry and weapons for this set in the Dwemer motif style.