Over 200 years before Agatha's time, the "greatest Spark of the time" created a masterwork for The Storm King, Andronicus Valois: nine incredibly advanced clanks known as The Muses. The Muses had abilities to perform before an audience and create feedback to enhance or alter the audience's collective mood. The spark's name was Van Rijn, whose full initials were RvR.
After Van Rijn's death, many people wished to study the Muses, but the work was extremely delicate. This didn't seem to stop anyone and several of the Muses were tragically destroyed. Only three escaped for certain, and one of those just barely.
Other Van Rijn works existed but have not yet been revealed. Agatha's acclaim (having learned from the then-current Van Rijn expert, Dr. Tarsus Beetle), indicates that any of the other creations would be as nearly magical.