Part of the Rotmender's Raiment set:

The set gives these bonuses as more pieces are worn: 2: +5 Shadow Resistance. 3: +10 Intellect. 4: When your Mana falls below 15%, restore 200 Mana over 10 sec. Restores twice as much Mana in Haunted and Wasteland areas. May only occur once every 5 min. 5: Grants your healing spells a chance to heal for an additional 40 Health every 3 sec for 15 sec. Set Details | All Sets