Mirakuru (ミラクル, lit. as Miracle) is a Japanese super-soldier serum that causes enhanced physical strength, speed, endurance, durability, agility, stamina, reflexes, and an accelerated healing factor once injected; however, its use is dangerous, as the serum can easily prove fatal if not correctly administered.
Its exact effects are unclear, though so far every individual injected with the serum has begun bleeding from the eyes immediately after injection. If the subject survives, they awaken after a few hours with the serum in full effect with strength, endurance, durability, agility, stamina, reflexes, speed, increased to superhuman levels; in addition to a healing factor. The Mirakuru also enhances the user's senses, as Slade was able to smell the TNT that was planted in an attempt to kill him. In order for the serum to work properly, a sedative must be administered along with it, otherwise the recipient will die. However, in some cases a subject can survive the Mirakuru injection without the sedative, as demonstrated with Slade Wilson and Roy Harper. Sebastian Blood takes advantage of this as a form of natural selection, to allow only those "worthy" serve him whereas those who aren't worthy, die.
According to Sara Lance, the serum has serious side effects even on those who survive injection, either deforming their bodies or warping their minds. A person can keep themselves from completely losing their control with intense focus. The Mirakuru's ability to drive a person to insanity appears to occur as a hallucination, which takes on the form of the person the victim cares for most and tells them to commit horrendous acts.
According to Anthony Ivo in "Keep Your Enemies Closer", the Mirakuru was a serum that caused increased strength and rapid cell regeneration created by the Imperial Japanese Army during World War II, in hopes of creating an army of super soldiers. They transported their only supply by submarine, and when it was under heavy fire by the Allied Forces, it ran aground on Lian Yu. After Ivo's men invaded the island, they were slaughtered by Oliver, Shado and Slade. Because of the picture they had, he managed to find the cave they were seeking. In the cave, they found a number of bodies of Japanese World War II soldiers, all with deformed skulls. Next to the body was a Hozen with scriptures. Some time later, Oliver was kidnapped by Ivo, and forced to take him to the Hozen. After an ambush, Oliver and Sara were rescued by both, and they discovered a series of coordinated proceedings of the stone. When they reached the abandoned submarine, Oliver found a box with several injections containing Mirakuru, and so they inject in Slade, who was dying, due to previous injury, even without the necessary anesthetic. After Slade's apparent death, Ivo's goons found the submarine and collect the serum, as well as taking Oliver, Sara, and Shado as hostages. Hours later, Slade awakened, his wounds healed completely, and with massively enhanced abilities. After running up to Oliver and others, Slade used his abilities to kill all of Ivo's men.
Sometime later, Ivo tested the serum in several men, however all died. Oliver also managed to recover the remaining samples, and burned them. Slade later offer his blood to mass produce the Mirakuru to Sebastian Blood, who used it to create an army of superhumans. Unlike Oliver and Slade's relationship, Sebastian is somehow able to maintain control over men he injected with the Mirakuru.
In "Crucible", Xavier Reed is captured by Brother Blood and injected with Mirakuru; he dies after bleeding from his eyes, unable to control or resist the effects. Also, Sin's friend, Max Stanton was found in an alley, dead with blood running out of his eyes, revealing that he was injected with the serum, but was unsuccessful and died.
In "The Scientist", Cyrus Gold is shown to have super strength and superhuman durability, as implied by the drug's assumed effects. Furthermore, while he defeats Oliver twice, Oliver claims he has beat at least one user of Mirakuru on Lian Yu. He also states that all of Ivo's test subjects are dead, and that he burned the rest of the serum that they found on the Japanese submarine.
In "Three Ghosts", it is shown that Sebastian Blood recreated Mirakuru using samples from Slade Wilson's blood. Also, Brother Blood forcefully injects Roy Harper with the serum, causing his eyes to bleed until he dies. Oliver though is convinced by a hallucination of Tommy Merlyn to keep fighting and he manages to kill Gold by blowing up the centrifuge, spilling chemicals all over him. Oliver then manages to revive Roy. Later, while resting, Roy discovers that the wound on his knee from where Arrow shot him is completely healed.
In "The Promise", Sara and Oliver burn the box that the Mirakuru belonged in, believing the Mirakuru to be inside it, it is later revealed that Slade hid it, and kept it on him in case he needed it.
In "Deathstroke", during a meeting with Slade Wilson and Sebastian Blood, Isabel Rochev explains that since taking full control of Queen Consolidated she has devoted all resources of Queen Consolidated's applied sciences division to mass-producing the Mirakuru.
In "The Man Under the Hood", Team Arrow blows up Queen Consolidated's Applied Sciences Division, forcing Slade to find an alternative means of administering Mirakuru to his army of prisoners. He captures Roy and steals a "bio-transfuser" from S.T.A.R. Labs and uses it to transfuse the Mirakuru from Roy's blood into the prisoners. The Arrow interrupts the process and rescues Roy, but Slade manages to use his own blood to successfully infuse Isabel Rochev and the prisoners with Mirakuru.
During the island flashbacks, Ivo reveals that he created a cure that could reverse the effects of the Mirakuru and gives Oliver and Sara the key to the safe where it is hidden. In the present day, Oliver steals a sample of Mirakuru from Slade and gives it to Felicity, who asks Cisco Ramon and Caitlin Snow to help her analyze it and synthesize the cure.
In "Streets of Fire", S.T.A.R. Labs successfully finishes creating a cure for the Mirakuru. After the cure was stolen in transit by Slade Wilson, Sebastian Blood steals it from Slade and gives it to Oliver after Sebastian realizes Slade wants to destroy the city. Oliver begins to administer the cure to Roy but hesitates wondering if it might kill him. When Amanda Waller tells him she will destroy the city if he doesn't stop Slade and his army by dawn, he decides he's running out of time and that he needs Roy and not just for himself but for Thea as well, and injects him with the cure.
In the island flashbacks, Oliver rescues Sara from the Amazo and attempts to get the cure to use on Slade, only to be captured by their former friend, who shows them he has already taken the cure out of the safe.
- Cyrus Gold (deceased)
- Roy Harper (unwilling; cured)
- Isabel Rochev (deceased)
- Slade Wilson (used to heal injuries; cured)
- Iron Heights prisoners (cured)
- Japanese soldiers (deceased)
- Main article: Mirakuru cure
It has been proven possible to develop a cure for Mirakuru. One was previously developed by Anthony Ivo prior to 2009 and another by S.T.A.R. Labs in 2014. The first time, Oliver Queen was given the choice between killing Slade Wilson and curing him, opting for the former (only to later find he had not been killed). In 2014, Oliver and his team mass-spread the cure through arrows they shot in to Mirakuru-enhanced soldiers, curing them all. Felicity Smoak also injected it in to Slade, causing him to finally be rid of superhuman abilities.
- "Keep Your Enemies Closer"
- "State v. Queen"
- "The Scientist"
- "Three Ghosts"
- "The Promise"
- "The Man Under the Hood"
- "Streets of Fire"
- In the comics, Deathstroke was injected with a experimental serum by the US government which left him in a coma for months. When he awoke the serum had enhanced his body giving him the strength of ten men along with heightened speed, agility, stamina, and reflexes. It also increased his capacity to use up to 90% of his brain at any one time. The serum also provided him with a healing factor in his blood that enabled him to heal from physical injury much faster than a normal person; however, it did have limitations, as he could not heal his missing eye and was unable regenerate entire limbs.
- Mirakuru is similar to other drugs used in DC comics such as Venom, a steroidal compound used by Bane to enhance his strength. Venom was derived from Miraclo, a serum used by the hero Hourman which lasted only one hour. Another serum used in the comics was Blockbuster, which permanently enhanced Mark Desmond and his brother Roland Desmond into hulk-like monsters.
- The drug's regenerative powers and negative effects to the recipient's psyche makes it similar to the RL65 serum from Smallville.