Brigid the Dragon & King Arthur's Coconuts

When not looking for human parties to crash or otherwise being entertained by the activities and creativity of lesser beings, the ancient red dragon known as Brigid in her human form spends much of her time creating quirky magic items. She either gives these away as presents, or places in the path of treasure hunters in the hopes they'll be mistaken for important artifacts. This is her latest creation.

 
KING ARTHUR'S COCONUT SHELLS
This item consists of two parts, each of which resemble gold-plated half coconut shells. At first glance, they appear to be a pair of odd ashtrays--and they certainly can be used as such--but they are far more than that. When examined using Detect Magic, the half-shells both radiate strong Alteration/Transmuation magic.
   Functions: When each half of "King Arthur's Coconut Shells" are held in one of the user's hands, and then clapped together in a rhythmic fashion, a sound similar to that made by the hooves of a trotting horse. So long as the user keeps making a clip-clop sound with the shells by striking them together, he or she and one other target can travel at a speed of 10 miles/hour across any terrain a horse would be able to traverse. The user must keep a continuous beat or the rate of travel will slow and the pair will come to a stop within two rounds, just as if they had pulled the reigns back on horses.
Neither the user nor the targeted second person become fatigued while under the effects of the "Coconut Shells", but the user must make a Fortitude saving throw (DC13) every hour. If the roll fails to match or exceed 13, the users arms are sore, the beat becomes unsteady and the rate of travel is reduced to 8 miles/hour. If the check fails at the end of the next hour, the rate of travel is reduced to 4 miles/hour. A third failed check means the "horses" need rest, and the pair must take a break of at least an hour.
   Trivia: This magic item was inspired by one of Brigid's favorite movies, "Monte Python and the Holy Grail". She's not sure what she'll do with this creation. For now, she's having fun, in human form, trotting back and forth across the rocky plains near her home in northern Arizona.