Headband of Swift Thought

Full Item Description
The Headband of Swift Thought is a simple band of silver, shaped to fit around the head of a humanoid; a minor enchantment worked into the quartz crystal adorning the front of it allows it to fit most humanoid creatures of roughly human size, but the true wonder comes from the potent magic in the metal itself.
When worn, the headband provides a focus for the mental energies of the wearer, transforming it into an acceleration of the wearer's limbs to grant them greater speed. The exact degree of the enhancement depends on the intellect of the wearer, however, and it does have a minor drawback - the greater the increase in speed, the more reduced the wearer's mental abilities becomes.

History
First created in a much more effective form by the mystic Xelhan of the Phaedran Empire, the Headband originally only provided a specific, fixed increase in speed - enough that Xelhan could keep up with his swift companions rather than being forever left behind. The original headband does not draw enough mental energy to reduce the wearer's intellect, but later incarnations - crafted by other mystics who were of the opinion that if a little extra speed was good, more speed was that much better - draw on so much of the wearer's intellect that the increased speed simply makes for a fast-moving imbecile.
The original headband has long since been lost, presumably interred with Xelhan when he died. Later versions remain in circulation, however, as many people find them on the remains of the unfortunates who wore them before, and never recovered enough wit to pull them off before they did something foolhardy, such as trying a running jump over a wide canyon.

Magic/Cursed Properties
The weakest version of the headband simply increases the movement rate of the wearer by a small amount - no more than ten percent, at best.
Stronger versions provide greater boosts in speed, but begin to draw on the intellect of the wearer. For every ten or fifteen percent of speed, the overall intellectual ability of the wearer is diminished by an equal amount. Eventually, the swiftest headbands result in drooling idiots who can outrun the wind - usually headfirst into a wall to die.