Gossamer is a light armor set. When you heal yourself or an ally, you grant them Major Evasion for 2 seconds, reducing damage from area attacks by 25%.
The Gossamer 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 light armor, weapons and jewelry of this set in the Silken Ring motif style.