In addition to the part they'll play in the larger setting, I wanted an item that could be slowly assembled and quested for, and something that could be a part of any end-game.
In ancient times, before the gods took notice of the Material Plane, it was the playground and feeding place of demons. These demons would torment and abuse the young human race for sport. After many years of demonic attacks, a group of powerful wizards formed what would much later become known as the First Guild. To defend their settlements, they created a Runic Orb of tremendous magical power, composed of separate pieces. Each piece was held in trust by a high-ranking member, but could be magically and magnetically interlocked with the others. In this way the great power of the Orb could be shared and was prevented from being used without democratic consent. Were it to be used too often by one person, the incredible power contained in the sphere would drive even the most well meaning of souls to madness. Legend says that for this reason, the original Great Orb was eventually destroyed, although some say it can never be destroyed - only deconstructed into its parts. In any event, its possible whereabouts and specific powers are unknown now. Similar (but less powerful) Runic Orbs are said to exist, rumored to be buried in forgotten tombs or disassembled and strewn throughout ancient ruins. The knowledge of their construction seems lost forever.
Powers, Use, and Vulnerability
There are two kinds of Runic Orbs: Greater and Lesser. A Greater Orb comprises twenty- four interlocking pieces, each piece inscribed with a single rune (or other type of magical glyph). They are approximately twelve inches in diameter, and weigh about twice that number in pounds. Lesser Orbs are similarly constituted, being but six inches in diameter when whole, weighing about twelve pounds, and of only twelve interlocking pieces. The pieces that make up an orb are made from a metal that appears to be cast iron, but that is resistant to rust and virtually indestructible. Both types of orbs and individual pieces are black as coal. When fully constructed and touched by human hands, they become illuminated from within (treat as Continual Light spell).
The powers of Runic Orbs are varied, but are magically linked to the lunar cycle. During the waning cycle, the power of the orb is limited to diminishment. Dispelling, destruction, darkness, silence, invisibility, removal, confusion, restriction of movement, fear and bewilderment - these are the domain of a Runic Orb’s powers during this time. Conversely, during the waxing cycle, creation, light, protection, curing, finding, enhancing movement, and growth are examples of the power of the orb.
Only the magic user class can utilize the power of Runic Orbs: Lesser Orbs confer up to twelve levels of spells per day, Greater Orbs up to twenty four levels. Although these spells are unchangeable, they vary from from one orb to another, and also vary based on the lunar cycle. For example, during the waxing moon a Lesser Runic Orb might contain the 2nd level spell Locate Object, the 4th level Plant Growth, and the 6th level Reincarnation. During the waning cycle the same Lesser Orb might contain the spells Hold Portal, Confusion, and Mass Invisibility, or even just twelve instances of Sleep.
When holding an orb, the magic user is suddenly aware of the item's spell-conferring abilities, and as occurs with his own spells, forgets them once they are cast. These orb- derived spells are then unavailable until a full day later. Unlike magic scrolls, an orb cannot be used as a way to learn new spells. A Lesser Orb can be held in one hand while the other wields a weapon or is involved in spell casting. A Greater Orb must be held with both hands to be used.
Although the pieces of Orbs are indestructible (even by the use of a Wish spell ), an Orb itself has a hit point value of d4 x12 (Lesser) or d4 x24 (Greater) and an Armor Class of 0. If the hit point value of an Orb reaches zero, the magnetic power of its parts fails, and it will fall apart, effectively removing its power. The magnetic attraction of the parts to one another will not return again until a full day has passed. This attraction only adheres the pieces to one another once they've been placed into physical contact - it does not work over any distance.
Runic Orbs and pieces of them are only solid for and can only be handled by natives of the Prime Material Plane and cannot be transported by any means to other planes.
The Curse of the Orbs
The power of the orbs is mighty indeed – but its creators wisely ensured that its use carry a price. If an orb is used on more than one day in a month's time, a saving throw must be made per additional day of use. Failure to save results in a permanent loss of wisdom points. See the table below (Greater Orbs penalties in parentheses).
Note: Non-magic user classes/races are not affected by this as they can't use these items. Optional exception: even attempts by halflings (curse them!) to use these items will be penalized as per magic users.
Wisdom lost in this way may not be restored by any magical means. Reduction in Wisdom to less than 3 effectively removes the player character from play, as at this point the PC will be a raving lunatic.
Parts of Runic Orbs may be interchanged with the parts of other Runic Orbs, but there is no clear, predictable outcome - the abilities of the orbs may stay the same but may change dramatically and at random. It's also unclear if a specific arrangement of the pieces of a particular orb will to empower it with specific abilities. It’s said, though, that certain ancient scrolls and magical tomes record theories and purported explanations of the science and power of the orbs. If such knowledge was recorded, it's most likely lost to antiquity, or very heavily guarded indeed.
Very high-level magic users and the Elven Kings know that there are twelve Lesser Orbs for each of the Greater Orbs and some believe that the mystery of the original Great Orb is contained in these others. Since the supposed destruction of the Great Orb, demonic attacks have increased in numbers and regularity. There are those who consider the reunification of The Great Orb to be possible and actively seek for its pieces. Some note with interest that the Gods only revealed themselves to Man after the creation of the Great Orb. Perhaps some of them feel threatened by the very existence of such a relic and compel their followers to quest for pieces of it, although given the Earth-bound nature of the pieces, what purpose they might have is unclear.
The Great Orb
I wasn't aware of runic orbs elsewhere until I began hunting a little for art components and discovered that they're apparently found in WoW (I've still never played it). I suspect these items bare little or no resemblance to the items in that game though.
Re: artwork above, I have a new respect for the artist behind the wikipedia icon, which I obviously (!) borrowed, removed symbols from, texturized and darkened, and inscribed with the elder futhark by hand. Attempting to create a decent similar item with the proper number of (12 or 24) pieces was a frustrating exercise, but the image of the Lesser Runic Orb (above, top) is an example.