- "You had a gift. An unbreakable weapon that fell from the sky for you to use. For you to control."
- —Grace Gibbons to Orlin Dwyer[src]
The lightning dagger was a piece of meta-tech and the primary weapon used by Orlin Dwyer (David Hersch in an alternate future) in his rampage as Cicada. It was owned by a future version of Grace Gibbons, after she took on her uncle's mantle as Cicada. The lightning dagger was later sent to the Mirrorverse by Barry Allen.
When the S.T.A.R. Labs satellite was knocked out of orbit by Clifford DeVoe following the failed Enlightenment, pieces of the satellite (which DeVoe had loaded with dark matter) impacted in 46 different locations. Cicada's dagger was a piece of shrapnel from the core of the satellite, where the dark matter concentration was the highest.
The shrapnel hit David Hersh, damaging his lung and giving him a breathing problem. The bit that broke off became his go-to serial killer weapon as he went on a rampage before finally disappearing from the public eye. See erased timeline for what happened to dagger
The dagger is the same piece of shrapnel that gave Orlin Dwyer the wound in his chest. (Though, in an erased timeline, it's implied to have struck David Hersch instead, leading to Hersch becoming Cicada in place of Dwyer.) As a result, he became connected to the weapon; allowing him to call it to him across any distance due to the fact that he obtained his powers alongside it. The dagger then became Orlin's signature weapon to kill meta-humans in his mission as Cicada.
After Team Flash used their meta-human cure on Orlin, his bond with the dagger was severed. However, at some point after she awoke from her coma, Grace took on the mantle of Cicada to continue her uncle's legacy after he was cured. Eventually, Grace traveled back to March 2019 to S.T.A.R. Labs (the time and place Orlin was given the cure) to rescue her uncle after he took the cure, though she was too late. A battle between her and Team Flash ensued, taking them all out, she killed Dr. Ambres with Orlin's dagger (which Grace herself seemed to have bonded with) and took an unconscious Orlin to a cabin in the woods to be healed.
Ralph couldn't figure out why Eobard Thawne was so keen to help Nora stop Cicada, insisting that they'd have to destroy the dagger in order to defeat the serial killer, since Cicada II didn't have the dagger in the future (in which Team Flash never managed to defeat her). Ralph then realized that the dagger is Eobard's plan. He subsequently kept Barry from destroying the dagger when they first had the chance to do so, fearing what would happen if they did destroy it.
Sent to the Mirrorverse
As Grace was about to kill Nora, Barry used the mirror gun to eliminate the dagger to ensure his daughter wouldn't be murdered. Future Grace watched as the dagger disintegrated to nothing before she herself was erased from existence, as her younger self decided never to be the serial killer she had seen herself become. The dagger, in fact, was transported to the Mirrorverse, where it was later found by Kamilla Hwang, who began running tests on it.
In the original timeline, the piece of shrapnel that became the dagger gave David Hersch his powers, and he became Cicada at some point after 2018. Sometime after Hersch's disappearance (or, in another alternate timeline, the disappearance of Orlin Dwyer), the dagger somehow ended up in Iron Heights Prison and was strapped to Eobard's chest, dampening his powers while he sits on death row. However, due to Thawne's meddling with the timeline, this never happened.
- Electricity generation: Cicada's dagger can also generate red electricity.
- Force-field generation: When the dagger lodges itself into the ground, it generates a force-field of red energy.
- Meta-human detection: The dagger glows red if a meta-human who gained powers due to exposure to dark matter is near.
- Psionic bond: The dagger shares a psychic connection to Orlin Dwyer (and later Grace Gibbons), as it originated from the same satellite which gave him his powers. Orlin can mentally summon the dagger to him from any distance; even if it's been sent as far away as outer space; and is the only individual who can use it. In the future that an older version of Grace comes from, she too gains a connection to this dagger, being able to summon it back to her from great distances.
- Power negation: The dagger has the ability to negate meta-human powers within its presence. The dagger has the ability to generate a field that negates all other meta-human powers. Even if a meta-human regains usage of their powers afterward, there will be a period of time where the powers remain severely weakened and long enough exposure to the dagger can potentially remove the powers permanently.
- Larger quantities of dark matter: Team Flash were able to temporarily negate the influence of the dagger by imbuing a piece of metal with a higher concentration of dark matter energy.
- Mirror gun: After being tested by Cisco on the satellite core from which the dagger originated, successfully obliterating said core, Team Flash concluded that this weapon can in fact destroy the dagger to which it actually transport it to the mirrorverse. They later send the dagger into the mirrorverse using the mirror gun.
- Non-dark matter-based powers: The dagger is only able to negate the powers of meta-humans specifically created by exposure to dark matter. Caitlin Snow's Killer Frost powers can still manifest in the dagger's presence, since she gained her powers through other means.
- The dagger glows when a dark matter-empowered meta-human is nearby, similar to the way that Elvish blades, such as Glamdring, Orcrist, and Sting glow when orcs or goblins are near in The Lord of the Rings.
- The dagger being able to be summoned back to Cicada's hand is very similar to Mjolnir, the mystical hammer owned by Thor from Marvel comics.
- For some unknown reason, the existence of the dagger on Earth-1 held off the Crisis for five years.
Behind the scenes
- In the comics, the Cicada's Daggers are two blades capable of absorbing the life force of his victims to be transferred to resurrect the dead.