Tang Chen is one of the paragons of the Douluo continent. Long before Tang San's birth, he had already reached the 99th rank. While travelling with the equally-ranked Qian Daoliu, Spirit Hall's Supreme Elder, he came across Sea God island. There, Qian Daoliu and him successively challenged the Great Priestess Bo Saixi, whose spirit rank had also reached the peak. Shockingly, both of them lost to her. Bo Saixi later explained that Qian Daoliu reigned supreme in the sky, she in the sea and Tang Chen on land.
Having fallen for Bo Saixi, Tang Chen and Qian Daoliu tried to woo her. She replied by declaring she'd accept the one who'd reach Godhood first. Although it might have seemed like she did not care for one over the other, Qian Daoliu and she, both divinity guardians, had attained their cultivation ranks through external means whereas Tang Chen was the only one who'd reached the 99th stage on his own and, thus, the only one able to attain godhood. Therefore, Tang Chen was regarded as the most talented spirit master of his generation.
Dead set on obtaining Bo Saixi's favor but unable to accumulate his own faith, Tang Chen had to find a god's inheritance. In addition, his proud heart did not allow him to return without completing his promise. He finally found one in Slaughter City where took place the Asura God's trial. While confronting the eight trial, Tang Chen's mentality was tainted by the Rakshasa God's depravity and became parasited by the Blood Red Nine-Headed Bat King, his opponent in said trial. This led to Tang Chen becoming the Slaughter King of Slaughter City.
Later on in the story, the Slaughter King had been poisoned by Tang San. When Tang San returned from Sea God island, the Slaughter King pursued him in order to obtain the antidote. Facing the Slaughter King's evil and depraved domain, Tang San unleashed his righteous Sea God's Light upon him. Unbeknownst to him, the Sea God's power weakened the parasite's hold on Tang Chen, which allowed him to breakthrough and regain his freedom. After talking with Tang San and learning of the current state of the Clear Sky School and of the Douluo Continent, Tang Chen chose to go Sea God island and join Bo Saixi's side although his expression showed real worry for the clan. Before leaving, having recognized Tang San's talent, Tang Chen passed onto him his personal identity token. With this item in hand, Tang San received authority surpassing that of the Clear Sky School elders and sect master.
Back on Sea God island, Tang Chen accompanied Bo Saixi three more days before passing away. The Blood Red Nine-Headed Bat King's poison had long since corroded his strong body. He'd been able to persevere while parasited because his power wasn't too strong but, as soon as his mind awakened, so did his own tremendous energy. That, coupled with a portion of the Asura god's power entering him, immediately shattered his body. At that point, Tang Chen endured as long as he could in order to once again see Bo Saixi.
Tang Chen left his Asura Sword as a memento to Tang San therefore allowing the choice between reaching godhood through either the Sea God's or the Asura God's inheritance. Indeed, when Tang San obtained his Death God Domain, he had actually completed the Asura God's first trial. As long as one had passed this trial, they had a chance to obtain Asura's godhood. Tang Chen's gift of the Asura Sword also meant a transmission of the majority of the Asura God's divinity as he was unwilling to simply his Asura God's power dissipate, he condensed it into the Asura Sword. Indeed, whereas the Sea God's effort were focused on a single successor, the Asura God's favor could be attained by multiple individuals. These chosens would then have to compete amongst themselves to obtain Asura's divinity. With Tang Chen's death, Tang San became the first successor candidate after obtaining the Asura Domain.
Before Tang San began truly his ninth trial, the Sea God promised him that he would help Tang Chen's damaged divine soul receive the qualification to pass onto the divine realm and accompany Bo Saixi's soul. Later on, the Asura God rebukes the Sea god by reminding him that Tang Chen was his successor and that he still had not decided whether or not he would heal his soul.