A set of five thick steel rings -- two small, two medium and one large -- linked together in a sort of chain. Script in a forgotten language runs along the inside of each. Beyond that, there is nothing whatsoever to mark these rings as special or magical in any way.
When the rings are worn properly (one on each wrist, one on each ankle and one on the head like a circlet), the bearer is completely protected from lightning and all electricity attacks. Indeed, they will tend to draw such attacks to them. Furthermore, after lightning has been absorbed by one of the rings, it will spread out around the user’s body to form a visible shield of electricity, which crackles around the wearer in a sphere. This shield will provide some safety against physical attacks by dealing damage to those that get too close, though it cannot actually block damage. Ranged weapons are still effective, of course.
By bringing the rings on both wrists together and aiming with his/her arms, the wearer may be able to intentionally discharge a bolt of electricity in a desired direction. This, of course, depends on whether the rings have received any charges from an outside source. The strength of this attack also depends on the strength of the stored charge, and using it will deplete the shield an equal amount.
The wearer will never be able to walk about during a thunderstorm undetected -- pretty much every bolt of lightning will be drawn unerringly to the user who will then build up a massive charge. There’s also a limit to how much of a energy this system can conntain, so expect the rings to start discharging in random directions after absorbing too much electrical energy. If the rings begin to glow blue, the point of random discharge should be close.
In a game with technology that relies on any sort of electricity, this set is going to be a major nuisance. The wearer will unintentionally soak in electricity from any source that is exposed, and may discharge accidentally into nearby electronics, cooking them as with an EMP pulse.
The Thunder Sphere has been linked to events of disaster and upheaval for much of the past three millennia, though no one is exactly sure of its origin. For example, during the Summer of Storms over a millennium ago, the Thundersphere is said to have caused the devastation of a whole battalion of battle-hardened troops, turning the tide of the Kings’ War.
In another instance, The Great Fire of Amestris was purported to have been started by a foreigner who was capable of shooting lightning from his fingertips. Legend says that the man was driven insane by the death of a close friend, and that not even the electric prods of the city guard could put him down. Half the city was in flames before he was killed by a stray arrow, but what happened to the Thunder Sphere after that is unknown.
The ring set looks nothing like a sphere, of course, and it can be fairly tricky to figure out how to get them apart at first. The key lies with the inscription on each ring. If translated poorly from the original language, the inscription on a given ring might read something like “Left Arm of the Thunder Sphere” or “Crown of the Thunder Sphere”. Sliding your hand through one of the “Arm” rings will cause it to separate from the other rings and constrict around the wearer’s arm, resizing itself to him. When the rings are worn properly and the lightning shield comes up for the first time, it should be plain that the user himself is the Thunder Sphere, not the set of rings.