The Spear of Destiny, or Holy Lance was an immensely powerful, biblical artifact capable of altering reality. It was mentioned in Judeo-Christian religions. It was an ordinary spear before the Roman soldier Longinus used it to puncture the side of Jesus Christ after he died on the cross, resulting in its immense supernatural powers. It could be found using the Askaran Amulet.
After the Legion of Doom used the spear to alter reality, Eobard Thawne destroyed it using a thermal reactor to incinerate it. When the Legends went back in time to stop the Legion from ever using the spear, it was ultimately de-powered by Sara Lance and then erased from existence along with Eobard Thawne, who was holding the spear when Hunter Zolomon killed him.
The Spear of Destiny was used in Jesus Christ's crucifixion.
In 1956, the Justice Society of America (without Obsidian) were sent by President Ike Eisenhower to Leipzig to retrieve the Spear of Destiny after supposedly being contacted by Rip Hunter. Deciding that the Time Masters couldn't be trusted with such a powerful artifact, they split the spear into four fragments, Rip sending the others into three different time periods with a member of the JSA for safekeeping, while keeping his own aboard the Waverider.
With a nearly-destroyed Waverider, Rip used his fragment of the Spear of Destiny to allow him to touch the ship's time drive. Due to this, he was transported to Los Angeles in 1967, where his memory was rewritten and he used the fragment as a prop in a film he was trying to make. Frustrated with the film, "Phil" had the props thrown out by George Lucas.
Sometime after helping The Flash undo Flashpoint, Eobard Thawne began seeking the Spear for his own purposes while teaming up with Damien Darhk and Malcolm Merlyn to change their respective destinies. After encountering the Legends in 1927 Chicago, the united Askaran Amulet showed the location of the Spear. The Legion of Doom proceeded to go to 1967, finding the location of Rip's fragment of the Spear. They almost had it, but were defeated by the Legends, who took it for themselves.
The Legion of Doom then had Rip's mind altered to become their ally, and was sent to 1776 where he killed George Washington to lure the Legends there so that he could get their piece of the spear. Rip managed to force Jax to reveal where the fragment was and took it for the Legion.
Soon after, Rip traveled into the future to Chicago in the year 3000, killed Charles/Dr. Mid-Nite and took the second fragment.
Later, the Legends traveled to the year 507, where they fought Damien Darhk and Rip Hunter in Camelot with the help of Courtney/Stargirl, King Arthur, Queen Guinevere and the Knights of the Round Table, and gained the third fragment.
Stargirl informed the Legends that Henry Heywood/Commander Steel had the final fragment of the spear but didn't know where or when he was, as they thought it would be safer if none of the team knew where Rip was taking them. After the Legends returned Rip's mind to normal, he told them that he knew the time and place in which Commander Steel and his fragment of the spear were; 1965 Manhattan.
After defeating Eobard Thawne in a space fight in 1970, Ray wins the fourth and final fragment on the moon. Then Thawne is jailed on the Waverider. He escaped only to be confronted by Ray with a gun. Thawne said that he knew that he, Eobard, was an aberration now and that he is pursued by a monster because of it. Thawne is warned, by his watch, that Hunter Zolomon is near and flees, leaving the Legends' two fragments of the spear behind.
Later, after the Legends discover that Eobard Thawne has been hiding from them outside time at the Vanishing Point, they take the Legion's two fragments, leaving Thawne furious. With the Spear of Destiny whole, the Legends search for the one thing that can destroy it: Christ's Blood in 1916 during World War I. Unfortunately, the Legion gain a new ally when Thawne and Damien Darhk recruit a version of Leonard Snart from before he joined the Legends. Faced with his old partner, Mick betrays the Legends, taking the Spear and joining his former partner and Legion of Doom. The vial of Christ's Blood is spilled during the battle. Then, back at the Vanishing Point, Malcolm Merlyn returns with the Calebros Manuscript to activate the Spear, allowing the Legion of Doom to rewrite reality.
After the Legion of Doom rewrote the reality, Eobard Thawne became Mayor of Central City, as well as Director of S.T.A.R. Labs with Martin Stein, Jefferson Jackson and Ray Palmer at his service and took Hunter Zolomon and Rip Hunter as his prisoners. Damien Darhk became Mayor of Star City and took Sara Lance and Amaya Jiwe as his Henchwomen, they killed Felicity Smoak, the last vigilante. Malcolm Merlyn is the leader of League of Assassins, his family are alive and Leonard Snart and Mick Rory control Central City. But Mick, seeing that he made a mistake in joining the Legion, takes Nate Heywood, who had became a conspiracy theorist, to re-assemble the Legends, with a mission to reclaim the Spear from Thawne before he destroys it, cementing the new reality. With the aid of Ray Palmer, Mick and Nate are able to acquire a 'gun' that allows them to restore Nate, Ray, Sara, Amaya, and Jax's memories, although Stein destroys the gun before it can restore him and the process does not restore Nate and Jax's powers. At the same time, Darhk, Merlyn, and Snart also form an alliance against Thawne to reclaim the Spear for themselves. In a fight to retrieve the Spear, Amaya, who attempts to restore reality, is killed by Snart, thus enabling Thawne to destroy the Spear. This traps the Legends in the new reality forever, without their special equipment, skills, or powers and apparently cementing the Legion of Doom's victory.
Later, however, the Legends are able to rescue Rip and traveled back to 1916, where they team up with their former selves to stop the Legion from ever using the Spear, although this results in Nate, Jax, Rip, and Mick being killed in the subsequent confrontation. Eventually, the past Sara Lance takes control of the spear and after seeing Laurel's spirit, which inspired her to do what's right, used the spear to disable its own powers so that Eobard couldn't use it, also releasing Hunter Zolomon, who killed Eobard, erasing their altered reality, as well as the spear itself, which Thawne had been holding, and erasing future Sara Lance, the only future Legend who hadn't been killed in the battle, who had traveled back to stop it.
Powers and abilities
- Reality alteration: The Spear can alter reality itself and allow the wielder to accomplish anything they desire, by speaking a certain phrase in Aramaic from the book of Kalabos. Eobard had used it to restore his natural existence and grant the wishes of his teammates. Eobard even comments that holding the Spear is literally like grasping Godhood in your hands. 
- Mystical Enhancements: For offensive purposes, the tip of the Spear can become filled with mystical energy which allows its user to cause great harm on potential targets. While using the Spear, Nate did this to defend himself from Eobard. The blow sent the speedster flying and knocked Thawne unconscious due to the severity of his impact against some lab equipment, suggesting that this energy turns the spear into something more akin to a club.
- Christ's blood: When Mick tried (and failed) to destroy the spear using his Heat Gun, a message appeared upon the spear, reading Natum De Sangine, Perditas A Sangine, which Nate was able to translate from Latin to English. It means Born of Blood, Undone by Blood. Nate then went on to explain to the rest of the team that just as the blood of Christ gave the spear its power, the blood of Christ is (allegedly) the only thing that can destroy it.
- Extreme heat: Wanting to ensure the Legion of Doom's alternate reality became permanent, Eobard decided to destroy the spear by alternate means. He determined that it was possible to destroy the spear by exposing it to heat levels even greater than the sun. To which, he had the altered-Stein design a machine to do so. However, it's unclear why the Heat Gun, which releases a stream capable of achieving absolute hot, was unable to destroy the spear. This could imply that the reactor may have somehow reached a temperature exceeding absolute hot, which could be enough to destroy a weapon such as the Spear of Destiny.
- Reality alteration: Should the wielder wish, the power of the spear can affect even itself, altering its own reality however the user desires, such as depowering itself.
DC's Legends of Tomorrow
Behind the scenes
In the comics, post-Crisis stories have stated that the Spear of Destiny was acquired by Adolf Hitler before the Second World War, using it to summon mythical Valkyries to fight for Germany. He later used to cast a spell that would render any Allied superhero under Nazi control if they entered territory held by the Axis, with the result that the Justice Society of America were forced to stay out of the front line of the war. Hitler attempted to use the Spear at war's end and call down the end of the world, but the Justice Society of America prevented this by trapping themselves out of time to fight the summoned gods themselves until the heroes were returned to reality.
The Spear survived the war's end, and was once used to try and bring down The Spectre, when that entity was out of control. Superman was given the Spear to accomplish this, but it had the side effect of giving him the personality of the Spear's prior wielder, being Hitler himself. The menace this posed roused the Spectre from his rage, and he freed Superman from the Spear's influence. It was subsequently banished to a pocket dimension, although a later storyline saw one group of mystics led by the sorceress Circe trying to acquire the Spear while another group led by Felix Faust used a fragment of the Spear to summon basic versions of the Norse pantheon, each plan being defeated simultaneously by the Justice League of America and the Justice League Elite (The Elite being a 'black ops' superhero team who deal with threats before they go public), with Wally West the only person aware of the dual efforts due to his membership on both teams.
- Historically, the Holy Lance, or the Lance of Longuinus is a legendary artifact supposed to be the lance that pierced the side of Jesus as he hung on the cross. The Lance was reported discovered in different places throughout history, but there is no definitive proof of the authenticity of those discoveries.