When it was still a province of China, Sin-Cong was a "hot spot" of political turmoil, where the Mandarin once attempted to eliminate C.I.A.'s influence on its non-democratic regime.
The Avengers were lured here by a fake distress call sent by the Commissar himself to crush them, hoping to win a propaganda victory. The country was eventually liberated once Scarlet Witch showed the witnessing townspeople that the tyrant was merely a robot and short-circuited it.
Believing the world was entering a super-powered arms race, the Commissar was inspired by the Avengers' origins to experiment on his citizens, sinking half of his treasury into efforts to make them un-humans.
When his son took control of Sin-Cong, he partnered with Hydra to supply their weapons and technology, gaining more money than ever to make his country a world power. Since then, Sin-Cong has been subjected to countless international sanctions for essentially being a military regime that only manufactured weapons for Hydra and human rights abuses.
The Terrigen Cloud hit the nation of Sin-Cong. One of the people their went through Terrigenesis was Thahn Ng. All the Inhumans were hunted down and burned alive in their homes by the nation's military by the ruling dictator of the nation.
As the Royal Inhuman diplomatic mission of Attilan approached his homeland and were greeted by the new Commissar of Sin-Cong the son of the previous Commissar. He welcomed them to his nation surrounded by giant robots and advanced military equipment, all of which was much more than the S.H.I.E.L.D.'s estimates.
However later aboard the R.I.V Thahn Ng bombarded the crew with the memories of all the deceased Nuhumans who were executed under the Commissar's orders in a bid to push them towards his goal of revenge. When Swain put herself into induced sleep in order to communicate with him/them, having a nice little chat where The Living Dream had deduced her true Nuhuman abilities due to his nature as an astral body, she then introduced Thahn to the central power core of the Vessel called Hub. Marveled and confused at how after reaching out to all the inhuman and Nuhuman minds aboard the vessel yet missed this being entirely. After the ship's captain explained to him the Hub's condition, the apparition quickly revealed his hand lashing out at both Nuhuman's possessing the ship's captain in order to commandeer its power source, siccing the entire travel worthy vessel upon the kingdom of his unjust executioner. After a lengthily battle where the R.I.V decimates Sin-Cong; easily flattening it's opposing Ariel craft, Thahn Ng takes great joy over the destruction and genocide his hunger for vengeance against his murderer has wrought. Swain does her best to resist but The vengeful disembodied entity completely digs his hooks into her being as well as Hub's just as Gorgon walked in on them all. Ordering Hubartes to fire the crippled Inhuman shifts his wheelchair into battle mode preparing to fight against the malignancy hosting the vessel's Captain. Enraged at this delay he asks why the latter is stopping him considering all that has happened to him and his fellow Inhuman's at the hand of the corrupt monarch. But instead of fighting Gorgon simply dissuades his rage by telling him how such ailments can drive one to distraction if not self-termination, and asks if he can truly sense those crippling emotions from everyone he has made contact with could he be strong enough to rise against them. Relinquishing his hold Thahn Ng departed Swain's consciousness and disappeared to parts unknown, eventually turning up within the body of the comatose head of the now deposed Commissar's father.