Negative Speed Force

"Breathe. You're reaching out and nobody's there. The loneliness is pain. Pain racing through your mind. Crushing you, wrecking you, shattering your soul into a million little pieces. And suddenly, you are no longer you. You're part of something different now. Part of a negative force."

- Eobard Thawne to Nora West-Allen

The Negative Speed Force is an extra-dimensional energy source fuelled by rage and hatred.

Overview
The Negative Speed Force is an extra-dimensional energy source that was used by the Reverse-Flash. Speedsters who have a Speed Force connection can gain a connection to the Negative Speed Force by using negative emotions such as rage, hatred, fear and anguish to the point where it corrupts them from the inside and will fuel their powers.

When using the Negative Speed Force, a speedster's natural yellow lightning and eyes will turn fully or partially red, and they will harness Negative Tachyons through siphoning them from the Speed Force to accelerate their own movement. This production of tachyons means that its users can be tracked more easily.

Original Multiverse
At some point, Eobard Thawne claimed to have created his own variation of the Speed Force, which he called the "Negative Speed Force", which is fuelled by negative energy and emotions to both prove his superiority as the Reverse-Flash and to travel through time without alerting The Flash to his presence. However, it was later revealed that Thawne was, in fact, chosen by the Negative Speed Force and the machine was merely a conduit for his mutation.

In 2049, Thawne taught Nora West-Allen how to use the Negative Speed Force to travel back to the present without alerting her father to her presence.

Thawne later revealed to Nora West-Allen and Barry Allen that it was part of his plan to allow West-Allen to connect with the Negative Speed Force as once Cicada's Dagger was destroyed she would be erased from the timeline. West-Allen eventually decided against going into the Negative Speed Force because it made her more like Thawne, and she was erased from existence.

New Multiverse
After the Crisis, Eobard Thawne's consciousness was transferred into Nash Wells' mind. Thawne connected to the Negative Speed Force in an attempt to stop Cisco Ramon and Cecile Horton from exorcising him from Wells' mind, but Ramon managed to place power-dampening cuffs on Wells' wrists just in time. Thawne promised that they would not be able to hold him when he gained full control of Wells' body, but he was eventually removed from his brain which resulted in him being trapped as negative tachyons.

Pre-Crisis

 * Reverse-Flash (Eobard Thawne)
 * XS (Nora West-Allen)

Post-Crisis

 * Godspeed (August Heart)
 * Reverse-Flash (Barry Allen)
 * Cobalt Blue (Eddie Thawne)
 * Reverse-Flash (Eobard Thawne)
 * Reverse-Flash (Eobard Thawne)
 * Zoom (Hunter Zolomon)
 * Joe West
 * Chillblaine (Mark Blaine)
 * Fast Track (Meena Dhawan)
 * XS (Nora West-Allen
 * Savitar (Barry Allen)

Red
The lightning of most users of the Negative Speed Force is red, due to the Force of Nature being a physical manifestation of negative emotions. The following are the speedsters who emit red lightning:
 * Reverse-Flash (Eobard Thawne)
 * Godspeed (August Heart)
 * Reverse-Flash (Barry Allen)
 * Cobalt Blue (Eddie Thawne)
 * Reverse-Flash (Eobard Thawne)
 * Reverse-Flash (Eobard Thawne)
 * Zoom (Hunter Zolomon)
 * Savitar (Barry Allen)

Red and Purple
Nora West-Allen's lightning was red and purple when she managed to run into the Negative Speed Force to return to the present day.

Black
Those with artificial connection to the Negative Speed Force will result in black lightning trails, similar to those infected with Bloodwork's blood. The following are the speedsters who emit black lightning:
 * Reverse-Flash (Eobard Thawne)
 * Fast Track (Meena Dhawan)

Blue
When the Negative Speed Force began searching for its next avatar, it concentrated its energy into a blue crystal. Those in contact and forced to be the force's avatar then gained blue lightning when using their abilities. The following are the speedsters who emit blue lightning:
 * Cobalt Blue (Eddie Thawne)
 * Joe West
 * Chillblaine (Mark Blaine)
 * XS (Nora West-Allen

Powers
Most powers granted by the Negative Speed Force and the same as those granted by the regular Speed Force with a few exceptions:
 * Reconnection: If a user of the Negative Speed Force loses their connection, then they can regain it by feeding on the negative emotions of others.
 * Temporal Bunker: The Negative Speed Force exists outside the timeline and so its users can avoid being erased from existence due to timeline changes by running and staying inside of it.
 * Undetectability: Users of the Negative Speed Force are undetectable by normal means by the users of the Speed Force.

Weaknesses
Most of the weaknesses of the Negative Speed Force are the same as those that exist for users of the regular Speed Force with a few exceptions:
 * Gravity: A speedster will lack the weight necessary to access their powers while exposed to irregular gravity.
 * Negative Tachyon Production: Users of the Negative Speed Force produce a massive amount of negative tachyons while running which can easily be tracked.