One of the few directly offensive Stream gears, Blast of Stream was first introduced in EFWQ V: Keys to the Hearts of the Sky Orbs to give Stream Elemenstors an actual useful offensive power. It manifests itself as an explosive beam of milky white light.
Purists of the original 13 books complained at first, until they realized that this meant that Stream now had a gear that could do something besides animate Furniture which actually made them almost useful characters in several other aspects of the franchise.