Hand of Mephala is a heavy armor set. When you take damage, you have a 10% chance to cast a web around you for 5 seconds, reducing the Movement Speed of enemies within by 50%. After 5 seconds the webs burst into venom, dealing 2580 Poison Damage and applying Minor Fracture to any enemy hit for 5 seconds, reducing their Physical Resistance by 1320.
The Hand of Mephala set is part of the Shadows of the Hist DLC. It drops in Cradle of Shadows in Shadowfen. Each set item is bound on pickup. You can acquire heavy armor, weapons and jewelry of this set in the Silken Ring motif style.