Yesterday at the Television Critics Association, The CW revealed that the mysterious "dark speedster" seen in the trailer for The Flash's forthcoming third season is in fact Savitar.
Described as a "Dark Master of the Speed Force," Savitar named himself after the Hindu god of motion. Here's the basics on the character, as provided by The Flash: Secret Files and Origins:
His original name unknown, Savitar was an Eastern Bloc military pilot who came to power after Jay Garrick's retirement and before Barry Allen's debut. Elected to test an experimental supersonic plane, Savitar became the fastest man alive -- and in that moment was infused with Speed Force energy that gave him super-speed.
A vicious and cruel man, Savitar believed that his power was a divine gift. Curious as to the nature of the Speed Force, Savitar extorted knowledge from other speedsters, including a younger Max Mercury.
Savitar and Max's battle catapulted Max forward in time and Savitar even further, giving Max years to assemble The Flash, Impulse, Jesse Quick, and other speedsters to combat the mad Savitar in final battle once he emerged from the time stream. In the end, Wally West defeated Savitar by pushing him into the Speed Force, which absorbed him.
Having studied ancient texts, Savitar knows more about Velocity's potential than any other speedster.
Unlike other speedsters, Savitar can absorb speed and motion, slowing objects down at will.
Some of that is more or less significant than other parts, of course -- but that last part -- that Savitar can use the Speed Force to slow objects (and indeed other speedsters) down is likely to play a big role in the season.
Savitar had a host of Speed Force-related skills, many of which Wally had to learn to master in order to beat him. Among them were the ability to protect himself in a null-inertia force field, and using speed to heal himself instantly (rather than just really fast like Barry does). In addition to being able to absorb speed, Savitar can "lend" speed and kinetic energy to objects or people, even those in a rest state, meaning that he could basically point at somebody and make them careen into a wall.
While Zoom and the Reverse-Flash operated relatively in secret in the first two seasons of The Flash and were a largely solitary threat, Savitar was actually the leader of a cult, the Thunderbolt Agents, who followed him without question.