The legacy all began with the child of Kataz. The Namek was in line to become Kami of Earth, but he needed to cleanse himself of the evil that still inhabited him to do so. This Namek split himself in two, one entity being filled with evil and the other side good. The good side was known as Kami-sama and the evil was Piccolo-Daimaou.
But first some slight background information on Piccolo-Daimaou. As you know he was Kami-sama's other half. In Dragonball (the series before Dragonball Z) Daimaou wreaks havoc on earth and is sealed into a jar by Master Roishi. Years later, Pilaf and his henchmen release Daimou from the jar (in hopes that Daimaou will grant Pilaf some land to rule over after Daimaou takes over the world). Piccolo Daimaou, instead of doing the dirty work himself, spawns 3 Namek-like creatures: Cymbal, Tambourine, and Drum. Daimaou orders them to go out and destroy all martial arts experts. Krillin and Roishi are both done in by the henchmen. Goku manages to defeat two of the spawn, and Yajirobe (yes, Yajirobe) defeats the 3rd. Goku, enraged at the death of his best friend Krillin, goes off to find Daimaou and kill him. In the meantime Daimaou gets control of the dragon balls.
After wishing for eternal youth, Daimaou destroys Shenlong the Eternal Dragon. Soon after Chiaotzu and Tenshinhan try their hand at keeping him at bay, but Chiaotzu was obliterated and Tenshinhan was only hanging in by a thread when Goku arrived once more.
Having drank water from the Sacred Well at the Tower before he came, Goku's power increased and faced off with Daimaou, only to defeat him and win by flying through his chest and creating a large, gaping hole.
This is where the Piccolo you know, came to be. Son Goku fought against Piccolo-Daimaou and in the evil Namek's last dying breath, he spat out an egg and whispered that his offspring would avenge his death. Thus, Piccolo was born.
Living up to his father's last words, Piccolo grew up intent on revenge. The Namek and Goku met up in the 23rd Budoukai where Piccolo was defeated. Piccolo trains until the begining of Dragon Ball Z, where Radditz arrives. Piccolo suggests to Goku that they team up to defeat the Saiya-jin (Piccolo has his own plans for taking over the world) and Goku agrees.
At first the alliance with Goku is uneasy, but as the story unfolds, their bond becomes stronger. During the fight with Radditz Piccolo first uses his Makkankasappo, which kills both Radditz and Goku. Piccolo doesn't mind that Goku is dead, but he has honor for one whom died so bravely. Piccolo stepped in to train Goku's son, Gohan for the upcoming battle against the other two saiya-jins that would arrive on earth, Nappa and Prince Vegeta.
At first the burly Namek was confused by the bond he found with Gohan and by his own actions, but Gohan brought out the good within Piccolo and their relationship grew stronger. In a deadly bout Piccolo saves Gohan's life by sacrificing himself and jumping in front of an energy blast from Nappa.
After dying at the hands of Nappa Piccolo goes to King Kaio's with Tenshinhan, Yamcha, and Chiaotzu to train. Piccolo and Kaio do not get along very well, but Kai acknowledges his power. Gohan and Krillin wish Piccolo back with the Namekian dragon balls during the Freeza saga. Piccolo goes to his "home-planet" for the first time. While on the way to re-join his allies on Namek, Piccolo comes upon Nail, a dying Namek warrior. Nail suggests that he and Piccolo fuse together--a permanent fusion. Piccolo grudgingly agrees, only because he wants to defeat the great enemy. After this Piccolo rushes off to fight Freeza and does very well, kicking Freeza's 2nd form's ass. Then Freeza went to his third form and things did not go so well. Vegeta was killed by final form Freeza and then Goku arrived after being healed in a rejuvination tank while everyone was off battling.
After Goku delivered the giant Genki Dama against Freeza's Death Ball the crew thought the fight was over, but they were wrong. Freeza climbs out of the rubble and then shoots a blast at at Goku, whom Piccolo shoved out of the way at the last minute, taking the hit, injuring him. Krillin was next to go at the hands of Freeza as he was incenerated from the inside out and blown to peices. Goku at this point turns super saiya-jin and Freeza and him fight some more. The Earth dragon balls are used (now that Kami came back with Piccolo) to bring all the people Freeza killed back to life and then transport everyone on the planet Namek to Earth, since the planet was collapsing. Everyone, including Piccolo, went back to Earth and awaited the outcome of the fight with Freeza.
Of course, we all know that Goku defeated Freeza. and...I can update this more as soon as I see more eps, you'll just have to wait until then...
But I CAN tell you that....in the future Piccolo fuses with Kami and for a short while in the strongest character in the series. Also in GT Piccolo and Dende kill lots of people to go down into hell and save Goku (it's my theory that if they can't make you look ugly in GT they kill you off). Dende is allowed back up on Earth, but Piccolo stays in some sort of limbo. More will be added as I see/learn of it.
Piccolo is the second strongest being on Earth. He wears a cape with weighted shoulder pads as constant training for his muscles. He is renowned for his powerful energy blasts as well as his ability to split into two or four separate entities. Green like a lizard, Piccolo also has the power to regenerate any limb that he may lose in battle and like all Nameks, doesn't consume food, out of some sort of ritual respect, but drinks only water.