Regeneration (再生, Sai Sei; lit. "Rebirth") is an ability that allows its user to replace limbs lost in battle and recover from similar severe damage. Piccolo is the first one to use this, displaying it during his battle with Goku.
Types of Regeneration
All Namekians are able to use the regeneration technique. This ability is first seen during the 23rd World Martial Arts Tournament after Goku redirects Piccolo's own Chasing Bullet back at Piccolo, which severely damages Piccolo's arm. Piccolo then proceeds to tear the injured arm off, to the horror of all the spectators, and regenerates a new one.
In the Vegeta Saga, the technique is seen again after Piccolo loses another arm from Raditz's twin beams which he regenerates after Raditz is defeated. During the Frieza Saga, Nail has his arm torn off by Frieza but regenerates it, much to the surprise of Frieza; in the English dub only, after seeing Nail regenerate his arm, Frieza decides that he will make a copy of the power to regenerate pieces of his anatomy and records it on his scouter. During the fight with Imperfect Cell, Piccolo has his arm drained by Cell leaving an emaciated brown stick. But Piccolo manages to distract Cell long enough to regenerate his arm back. Later on, when Imperfect Cell blasts a hole through Piccolo and throws him in the ocean, he can still recover thanks to his regeneration ability. Later still, in the Majin Buu Saga, Piccolo demonstrates that he can regenerate from any wound so long as his head is intact. Cell acquired the ability by being created in part by Piccolo's cells, absorbing that part of his Namekian makeup. On several occasions Cell regenerates from extremely severe wounds, including one which left no part of his body except for a single cell intact, implying that his regenerative nucleus exists in each one of his cells (this was not only thanks to this ability, as it a combination of Sai Sei and Frieza's ability to survive horrifically severe wounds and still live, even function). The head is where the "regenerative nucleus" (a.e. the regenerative organ) is located.
Lord Slug uses regeneration in the movie, Dragon Ball Z: Lord Slug. After transforming into a golden aura form of a Super Saiyan resembling a glorified Kaio-ken, Goku damages Lord Slug's arm. He then shocks Goku by tearing it off and regenerating a new one. Similarly, in the same movie, Piccolo rips off his own ears to avoid hearing Gohan's whistling tune (unbearable to Namekians' sensitive ears) but later uses Sai Sei to instantly grow his ears back, to everyone's amusement.
It is unknown if the regeneration is a basic part of all Namekians, since it may take some physical and mental training before Namekians can use it consciously. It also appears to be quite an exhausting procedure, every time after it is performed the user is breathing extremely heavily from the effort and strain, and requires absolute concentration of mind and body. It has been pointed out that regrowing limbs causes a severe temporary drain on the power level of the Namekian.
In Dragon Ball: Xenoverse, Namekian characters such as Piccolo or a Namekian Future Warrior will start regenerate health once it falls below 70%.
According to Daizenshuu, if a Saiyan's tail is removed, it will suddenly grow back if they are in danger, indicating that they have form of regeneration limited to their tails. Goku has regrown his tail several times throughout the course of the series, the first time was during the 21st World Martial Arts Tournament in his match against Giran and another during Dragon Ball GT where, after being turned into a child by Ultimate Shenron, his tail was growing back in, but needed help pulling it out. Gohan's tail also grew back during his battle with Vegeta.
Broly's stomach regenerates the hole that was punched through it by Goku seven years ago. In video games, when he returns as a Super Saiyan 3 after his second defeat, he is shown to have regenerated the injuries caused by the Family Kamehameha and the Sun. As Broly was never shown to regenerate on-screen, it is possible he found means other than regeneration to heal his injuries while in space.
Akami, the main threat in the Dream 9 Toriko & One Piece & Dragon Ball Z Super Collaboration Special, is able to regenerate its tentacles when they are damaged.
The Meta-Coolers have a similar ability, though it is more mechanical in nature and which is called Auto-Repair Ability (受動修復能力, Judōshūfuku Nōryoku) in Daizenshuu 7, Rebirth in the Budokai Tenkaichi series, and Revive in Dragon Ball Z: Supersonic Warriors 2. In addition to repairing any damage inflicted on themselves, their regeneration also corrects whatever design flaw allowed the injury in the first place and incorporates the correction in every subsequent unit. It should be noted that Meta-Cooler (the first encounter) is not the "real" Cooler (he is revealed to be one of many mechanical copies of the original Cooler; these "Meta-Cooler" bodies where created by the Big Gete Star), the "real" Cooler is the still living disembodied-head of Cooler that had merged with the Big Gete Star, with Cooler's head becoming one with its core. Like Frieza, Cooler has the ability to survive virtually any wound (like being sliced in half or decapitation) and function (as seen with both Frieza and Cooler). In addition, the real Cooler demonstrated a similar ability to Rebirth during their final battle, using wires to fashion for himself a new body during his final fight with Goku.
Cell is another bio-mechanical creature with regeneration. This is because he is programmed with the cells of Piccolo (and possibly having something to do with Goku's Zenkai). However, it is also implied that similar to Namekians, Cell's regeneration also results in a severe temporary drop in ki due to the stress of regenerating, although to a significantly lesser scale, as evidenced when, shortly after Cell regenerated from having most of his body being blown apart by Goku's Instant Kamehameha, Goku comments on Cell's ki decreasing in response to Cell's statement that Goku's ki had dropped from using the Instant Kamehameha. Cell can regenerate due to his Namekian cells, and thanks to Dr. Gero's gene-splicing and augmentation of his natural genetic abilities. Cell was shown to be able to take the destruction of his whole upper body at one point, and then later his entire body save a single cell, from which he was completely regrown.
Bio-Broly has a similar ability to regenerate, as seen when Krillin makes a direct hit to Broly's head with Destructo Disk, but it regenerates and reattaches to the body.
General Rilldo regenerative powers that can match (or even be higher depending on which state it is) to Meta-Cooler and Majin Buu, especially when he is in his Meta-Rilldo form. His regenerative powers are more effective in an environment where there are many metals. Baby's ability to liquefy grants him a form of regeneration similar to that of Cell, which allowed him to survive being seemingly obliterated by Goku, Trunks, and Pan on M-2. However, he is destroyed completely when Goku blasted him into the Sun. Rilldo's regenerative ability is called Metal Mending in the Dragon Ball Z Collectible Card Game.
Ghost Warrior Regeneration
Ghost Warriors are able to constantly regenerate from any attack thanks to Destron Gas. While regenerating, they turn into Destron Gas, move away, and then take their physical form back on.
Ghost Warriors Frieza, Cooler, Slug, and Turles possess the ability to regenerate in Dragon Ball Heroes.
Garlic Jr. successfully wished for immortality, and thus could not be killed under any circumstances. Any wounds he did take were healed rapidly as shown when a hole blown through his stomach regenerated in seconds with no hindrance to him whatsoever. When Frieza gains immortality in his scenario in the video game Dragon Ball Z: Supersonic Warriors, he restores his body to how it was prior to his injuries from his battle with Goku.
Majin Buu has the greatest level of regeneration in the series, allowing him to regenerate lost appendages, holes in his body, recover from being blown to pieces, or even being blasted to vapor so long as he is not completely atomized. In his case though, his entire body is in an unstable form and each singular piece of him, even as a fine dust, is able to reform back to his original shape. Super Buu's regeneration allows him to survive and regenerate after his Revenge Death Bomber Self Destruction technique. Buu's regeneration is not Namekian in nature, since he was able to regenerate wounds long before he absorbed Piccolo. However, Buu's regeneration has its limits, as after being beaten repeatedly, he starts to exert more to regenerate, while suffering from the wounds more. In Dragon Ball: Xenoverse, a Majin Future Warrior can regenerate their body after blowing themselves to pieces using the Ill Bomber Super Skill.
Janemba is able to heal almost instantly from the injuries Pikkon inflicted on him by insulting him. In the story of the PSP game Dragon Ball Z: Shin Budokai, when Super Janemba's physical form is completely destroyed, he is able to regenerate with a new body once enough evil energy clumps together.
Rage Shenron is also shown to be able to regenerate via Electric Slime in a very similar fashion as Majin Buu. Omega Shenron also gains the ability when he absorbs the Five-Star Dragon Ball which contains Rage Shenron's abilities.
Godly ki Regeneration
- Garlic Jr. (due to being immortal)
- Most Namekians
- Meta-Cooler (Nano-regeneration – Any injury Metal Cooler might suffer is instantly detected and repaired, and whatever flaws in his design that allowed the injury are corrected)
- Ghost Warriors (regenerate thanks to Destron Gas)
- Cell (taken from Piccolo)
- Majin Buu
- Super Buu
- Kid Buu
- General Rilldo
- Rage Shenron
- Syn Shenron
- Goku (In his Super Saiyan God form)
- Future Warrior (Majin and Namekian races only)
- 再 (Sai) - Again / twice / re-
- 生 (Sei) - Life / living / birth