Every time The Flash moves 4 units, he will receive one stack of speed force. Upon reaching 10 stacks, The Flash will activate the speed force, strengthening his next normal attack while dashing forward. He also temporarily reduces his target's movement speed by 50% and deals (+0) magic damage. When he hits his target, he gains a shield of 350 (+0).
The Flash deals additional damage when both dashes of the Super Speed hit, so you can do some serious damage if you plan ahead and time it right with Sonicboom.
Barry Allen was always moving a mile a minute—no one could ever get him to slow down. That changed the day his mother was murdered. Once a hyperactive kid who drove his teachers crazy, Barry’s energy was harnessed into a single-minded focus to find his mother’s true killer. His drive for justice led to a career as a forensic scientist, and he was completely absorbed by his work.
When a freak lightning bolt hit his lab, Barry was imbued with the power of super-speed, becoming the Flash. Now, he races up buildings, across oceans, and around the world to stop those who transgress against justice. With his ability to run at near light-speeds, Barry has discovered the ultimate adrenaline rush. Through determination and concentration, the Flash has been able to learn how to phase through objects, create sonic booms with the snap of his fingers—and never lose a race.
But the Flash’s abilities were put to the ultimate test by an unexpected event. As he attempted to save a group of children from a school fire, the Flash pushed his abilities to the limit, moving so fast that he approached the horizon of the speed of light. As part of his successful rescue of the children, the Flash tapped into the very heart of the Speed Force—the mysterious extra-dimensional energy that powered his abilities—and found himself swept into the Speed Force itself.
Awash in the flowing, morphing, hyper-dimensional currents of the Speed Force, the Flash catapulted through several alternate realities, until he found himself in a magical land called Athanor. At first, the Flash lamented being marooned in this perilous realm, but soon discovered that where the Speed Force is concerned, there are no coincidences. In Athanor, the Flash discovered that the Speed Force was being syphoned into Athanor by one of the Lokheim generals—resulting in the catastrophe that kept him trapped in Athanor.
The Flash has joined up with the rest of the Justice League members to uncover the mysteries of Athanor and restore the Speed Force. As he embarks on his quest, the Flash may uncover the true nature of his abilities—and this discovery will have ramifications not only for his own abilities, but for all the speedsters who have ever merged with the Speed Force.