With The Flash season 7 having come to a close, even some long-time fans of the show are struggling to recall every source of superspeed in the Arrowverse. The long-running superhero series has drawn deeply off the vast and often contradictory lore of DC Comics, portraying many of the different means people use to acquire superhuman speed. From experimental drugs to mystic forces, there are many ways to "ride the lightning."
Speedsters, it should be noted, are defined by their ability to move at unimaginable velocities. While there are many beings in the Arrowverse capable of moving faster than mere humans or even the proverbial "speeding bullet,' it takes a certain special something for a character to be considered a speedster. There's no hard numerical limit to this truism, as both Superman and Supergirl have proven capable of breaking the sound barrier. The difference is a thematic one, with speedsters drawing upon their power in unique ways to manifest abilities beyond merely moving fast, such as phasing through solid matter or the elemental control of lightning.
While speed is ultimately speed, each source offers various benefits and complications. Speedsters drawing upon an artificial power source, for instance, are inherently limited and cannot attain the ultimate velocity of an experienced organic speedster. This was what prompted the Godspeed War at the end of The Flash season 7, as the artificially empowered Godspeed sought out a source of organic speed and threatened The Flash's city until he could acquire one.
The Speed Force
Most of the speedsters across the Arrowverse originally drew power from the Speed Force before Crisis on Infinite Earths. Both an independent dimension and a fundamental source of energy, the Speed Force was comprised of tachyon particles that bonded with certain individuals. This selection was made by the Speed Force itself, which had an independent intelligence behind it; the Speed Force typically communicated with the speedsters that connected to it by manifesting in dreams or taking the appearance of the speedster's loved ones. In the case of Barry Allen, for instance, the Speed Force resembled his mother, Nora Allen.
The Velocity Serums
Originally created by the Hunter Zolomon of Earth-2, the Velocity serums are a series of drugs that temporarily grant a person access to the full powers of a speedster and the ability to tap into the Speed Force. The Flash season 2 saw Zolomon's formula further refined and enhanced by Dr. Harry Wells and Dr. Caitlin Snow, running through a number of upgrades from Velocity-6 to Velocity-9. The Flash season 6 introduced the most powerful Velocity serum yet, Velocity-X, in the episode "Death of the Speed Force," where The Flash used it to neutralize the time-slowing powers of the Turtle II. Frost later used Velocity-X in The Flash season 7 episode "The Speed of Thought" to temporarily give herself the ability to keep up with The Flash.
While the Velocity serums offer tremendous power, their effects are strictly temporary and, like most medications, continued use makes them less effective, as the body builds up a resistance to their effects. The earliest versions of the Velocity formula seemed to be addictive, leaving continual users with a need for speed, even beyond the naturally addictive rush of having a speedster's powers. The Velocity-9 formula was shown to be taxing upon both the body and the mind, causing scientist Eliza Harmon to develop a dissociative identity (the speedster thief Trajectory) and literally run herself to death, with her body completely degenerating at a cellular level. The Velocity serums are also uniquely vulnerable to radio waves and focused blasts can cause the bonds of the drug to break down much faster than normal, depowering the user in seconds. The first incarnation of XS used this Flash Fact to defeat the first incarnation of Godspeed in The Flash season 5 episode "Godspeed."
Negative Speed Force
Created by the Reverse-Flash Eobard Thawne to replicate the powers of Barry Allen, the Negative Speed Force utilizes negatively charged tachyons that latch on to the positively charged tachyons employed by Speed Force users. This allows Negative Speed Force users to siphon off the power of true speedsters, gaining access to the full range of Speed Force powers in the process. Negative Speed Force users can be identified by the fact that their lighting glows red and that the use of their powers leaves behind a trackable trail of negatively charged tachyons.
Negative Speed Force users have one notable power that separates them from true speedsters: they can prevent themselves from being erased by reality. It is speculated this is due to the Negative Speed Force existing apart from the natural laws of the multiverse and indeed being a perversion of those same laws. This is apparently what allowed at least one remnant of Eobard Thawne to remain despite the death of his ancestor Eddie Thawne in The Flash season 1 finale. Thawne said this connection could also have saved the life of the first incarnation of XS in The Flash season 5 finale as reality was rewritten so that her future never came to be, but she elected to die a clean death rather than depend upon the parasitic Negative Speed Force for survival.
Artificial Speed Force - Version 1.0
When the Speed Force began to die in the wake of Crisis on Infinite Earths, every surviving speedster on Earth-Prime began to slowly lose their powers. This led Barry Allen, Cisco Ramon and Chester P. Runk to construct an Artificial Speed Force based on the Negative Speed Force. However, to eliminate the possibility of emotional corruption (as the Negative Speed Force required its users to give in to their darkest impulses) Cisco Ramon employed an inert substance, an argon-xenon hybrid, to act as the core of the Artificial Speed Force. This had the unintended side-effect of increasing Barry Allen's cognitive abilities so that he could run calculations in his head faster than a quantum computer. Unfortunately, it also cut Barry off from his humanity, making him cool and calculating, and turned him against his allies in The Flash season 7 episode "The Speed of Thought."
Artificial Speed Force - Version 2.0
Going back to the drawing board, Barry Allen redesigned the Artificial Speed Force so that it would be empowered by positive emotions, such as the love he felt for his wife, Iris West-Allen, whom he used as a lightning rod to find his way home no matter how far across the Arrowverse he ran. The second Artificial Speed Force rejuvenated the original intelligence behind the Speed Force, in addition to restoring the powers of The Flash and every other speedster on Earth-Prime. However, it also led to the creation of three new Forces, the Still Force, Strength Force and Sage Force, and a reordering of the cosmos that sparked most of the complications presented in the first half of The Flash season 7.