Shroud of the Lich is a light armor set. When you cast an ability while under 33% Magicka, your Magicka Recovery is increased by 1032 for 20 seconds. This effect can occur every 1 minute.
Shroud of the Lich is a very popular Magicka recovery set for PvP players. It is easy to farm because it drops in the Crypt of Hearts dungeon which also offers several other very desirable sets: Ebon Armory for tanks, Leviathan for Stamina DD players, and the Ilambris monster helm (veteran mode only) which is very popular with Magicka DD players. Therefore it's not hard to find other players to run Crypt of Hearts with you, especially if you're part of an active guild.
The Shroud of the Lich set is part of the base game. It drops in Crypt of Hearts I and Crypt of Hearts II in Rivenspire. Each set item is bound on pickup. You can acquire light armor, weapons and jewelry of this set in the Lich (unique) motif style.