Mythallar

A mythallar is a spell engine which can produce continual spell effects over a very large scale, seemingly forever. The mythallar was invented in ancient Netheril by the arcanist Ioulaum, and was used widely throughout the Netherese Empire until its demise. The secret of its creation died with that empire, and none today know how to even begin to construct such a device.

Few believable records exist, but archaelogical ruins suggest that mythallars were spheres anywhere between 5 and 50 feet in diameter (the larger obviously corresponding to greater power), which would be placed in central, undoubtedly fortified positions within Netherese enclaves and cities. Historians believe that a mythallar, once put to purpose, would have been stupendously radiant, dangerous even to be near, and likely lethal to touch. They differ on whether or not the engines needed to be fed or fueled to maintain their effect, or if, somehow, they were simply perpetual energy machines.

The bards say that there are a very small number of mythallars to be found in the dark corners of the world, still operating, still full of terrible power, ready to be harnessed by the wicked, should adventurers not reach them first. But these tales are, of course, preposterous.