We learned in 5.3 that it has a data collection system installed in it that records the wearer's performance in combat; this is how they were able to install data into the new Weapons for the purpose of Oversoul.

Zenos' dark aura comes less from the armor and more from his legendary katana, Ame-no-Habakiri; during the first fight with him in Rhalgr's Reach he has only the Storm and Swell swords so the aura does not appear, and it isn't present in the second duel with him until he pulls out Ame-no-Habakiri. Most (if not all) of Zenos' magical abilities come from the use of enchanted weapons, though whether or not he's able to use magicks beyond Ascian-style teleportation hasn't been clarified.

As for the rest I presume they have some kind of cybernetic muscle system that enhances their wearer's physical strength, and with the right alloys can be made magic resistant. Other than that, what's the question?