These twin longswords deal an additional 5 elemental damage, whether or not the blow hits. The type of damage depends on which family the swords belong to. The set that Quarion recieved was of the Xixizar Family, and, therefore, deals lightning damage.
Each orb-bearer of the Six Families was given a set of matched swords, enchanted with the element of their Orb. These were forged during the Elder Days, on Utopia, and have been passed down through generations since.