Radiant Set is the highest grade armor set available in the game. Radiant set, which is Unique quality armor set, is dropped from Archdemons, Baels, and Deathlords in Death Valley.
Radiant armors provide set bonuses when worn in 2, 3, 4, or 5 pieces. To activate these set bonuses, the worn Radiant armors must be at grade +6 or higher.
Runes can't be added to Radiant armors.