At some point, Tian met and began dating Jinfeng. Though their relationship was considered forbidden by the Cold Peace, Shanghai's Shadowhunters and Downworlders were on good terms and they were supported not only by their families, but by the Conclave. Still, they typically tried to hide it from newcomers and keep out of prying eyes as the Clave would not be as tolerant.
In 2010, the Shanghai Shadow Market had two new regulars who seemingly came from no where. The Shanghai Institute took some interest in this and dispatched Tian to keep an eye on them as he knew the Downworlder Concession well. Tian kept a record of what they were buying and who they spoke to; all the while, they were watching him. Eventually the two warlocks cornered him and began threatening to expose his relationship with Jinfeng to the Cohort. When Tian realized that not only he would be punished but that his family would lose the Institute, he agreed to give them the information they asked for—on the Shadowhunters of China's defenses, Institutes, size, relationship with Downworlders.
Some time later, they confronted him once again but this time brought him to their headquarters. The warlocks identified themselves as Shinyun Jung and Ragnor Fell, followers of Sammael. They explained their plans to help bring their master back to Earth. They then told him that he too now worked for Sammael. When he refused, they reminded him that he had already provided them with intell and thus was a spy for Sammael. Though he tried to deny it, they threatened to tell his family what he had shared with them causing him to relent, feeling he had no choice.
The next thing they requested of him was a pheonix feather. They had intended him to betray Jinfeng and steal one of hers—giving Sammael control over her—but instead he confided in her and she was able to get him a feather from a long dead ancestor.
As an official servant of Sammael's, Tian was allowed access to Diyu. He decided to take advantage of the situation and learn the ins and outs of it, hoping it would prove useful if he were ever able to release himself from working for Sammael.
He got his chance when Alec Lightwood, Magnus Bane, and their friends came to Shanghai looking for Shinyun and Ragnor. He befriended the group and did his best to help them out. He provided them with shelter, information, and pointed them in the right direction of people who could help them. After he was revealed as a traitor in Diyu, Tian made to rescue Isabelle Lightwood, calling on Hu Shen. Together they made up with the others and showed Sammael that he was in fact his enemy. The group took shelter in the Xujiahui Cathedral of Reverse Shanghai.
The next day he and most of the group were subjected to the Hell of the Pit of Fire where they had to maintain their footing on moving platforms while demons attacked them. Magnus, Alec, and Ragnor had been taken elsewhere with Shinyun and Sammael. While they were gone, the group strategized and was able to keep the demons at bay and themselves alive. Upon their return, they were able to Portal to Shanghai from the crumbling world of Diyu. Before the group went their separate ways, Tian thanked Alec for being such an inspiration and swore to be involved and loud in order to make change in the Clave.
Tian is described as tall and wiry in build. He has straight-cut black hair and apparently dramatic-looking eyebrows. According to Alec Lightwood, he bears some resemblance to his distant relative Jem Carstairs.
- The Lost Book of the White (first and only appearance)
- He is an only child.
- He acts as a kind of older brother to his cousin Ke Liqin.
- Tian was trained by his grandmother Ke Yun.