Nail's History
Dragon Ball Z
Frieza Saga
When Dende takes Krillin to Guru's home to get his inner powers unlocked, Nail is there, who greets the two of them, but is cautious of Krillin's presence. Later on, while Gohan is getting his hidden powers unlocked by Guru, Vegeta arrives to collect a missing Dragon Ball. Nail confronts him and is ready to fight, with both of them insulting each other harshly. Gohan emerges with his newly unlocked powers before Nail and Vegeta had the opportunity to battle. Nail then senses five high power levels, which turn out to be those of the Ginyu Force. Guru orders Nail to go help the earthlings combat the Ginyu Force. Nail originally complies, and flies off to assist the earthlings and Vegeta, but before he arrives, he turns back to continue assisting Guru, and to protect him from Frieza, who came to know what is needed to say to make the Namekian Dragon rise from the Dragon Balls. Nail distracts Frieza and battles him in order to stop him from killing Guru, and from obtaining the secret password needed to activate the Dragon Balls for immortality. Due to Frieza having a minimum power level of 530,000, which is roughly twelve times that of Nail's, Nail is no match for the tyrant and loses an arm (which he regenerates) during the brutal battle. Frieza toys with Nail, and threatens to torture Guru, while insisting that Nail must divulge the password needed to summon the Namekian Dragon, Porunga. Before Frieza deals the final blow to Nail, Nail lets out a small smirk, and reveals that this fight was only a diversion to delay Frieza, so that Dende could get the Namekian Dragon Balls' password to the Earthlings. Enraged, Frieza immediately departs at full speed, leaving Nail to slowly die, broken and beaten.
Shortly afterward, thanks to the Namekian Dragon Balls, a newly resurrected Piccolo arrives on the planet and discovers the battered Namekian. Nail tells Piccolo that if Piccolo and Kami were one once, they would have beaten Frieza long ago. Nail asks Piccolo to fuse with him in order to increase his chances against Frieza, and at the same time save his life. Piccolo eventually agrees, after some questioning of Nail's motives, wondering if his personality will still be the same, to which Nail assures Piccolo his personality will not change, and he will still retain control. After they fuse, Piccolo's power level increases dramatically to the point of being even with that of Frieza's second form, and possibly even stronger (since Frieza made the decision to use his second transformation immediately after Piccolo removed his heavily weighted clothing).
In the English dub of the anime, when Piccolo fought second form Frieza, Piccolo revealed to Frieza that the two had fused while using Nail's voice. Later, When Vegeta found out about Dende's healing ability, he asked Krillin to inflict him to gain a Zenkai boost, Dende was hesitant to heal Vegeta until Piccolo told him to while using Nail's voice. When Dende is killed by Frieza in his final form, Nail was shocked and saddened. After everyone on Namek was brought back to life and transported to Earth, Dende finally realized that Nail had merged with Piccolo.
Cell Saga
Nail remained a part of Piccolo's being. Nail was heard via Piccolo's telepathic thoughts when Dende returned to Earth as its new Guardian of Earth during Cell's reign.
Majin Buu Saga
Nail remained a part of Piccolo's being. Nail is later seen in Piccolo's flashback to Dende describing fusion during Majin Buu's reign.
Dragon Ball Super: Universe Survival Saga
Nail and Kami made a brief motivational appearance inside Piccolo's mind while he was unconscious during the Tournament of Power. Along with Kami, he encourages Piccolo to keep on fighting for the sake of Universe 7 and its inhabitants.
