Shen Kuei is a Hong Kong based secret agent/mercenary who gained the name "The Cat" due to his stealthy, cunning nature. He is a former enemy and current rival of the Master of Kung Fu, Shang Chi.

The first time Shen Kuei met Shang Chi was when Shang was sent to Hong Kong to recieve documents Kuei had stolen on mission from the Chinese government. Kuei was no longer working for the Chinese when Shang arrived, and in fact had formed a relationship with a retired British intelligence officer named Juliette. Shang was told that Juliette's life was in danger from The Cat and arrived with the intention to rescue Juliette and retrieve the stolen British documents. Juliette cleared all of this up by telling Shang the location of the documents and requesting that he and MI-6 leave her and Shen Kuei alone. Upon arriving at the scene of Shang and Juliette speaking to one another, Shen Kuei mistakenly assumed Juliette had been a mole for MI-6, faking her retirement and her love to get close to him, so she could rat out his location to MI-6. Shen Kuei believed that Shang was a government assassin and began a heated, merciless fight that proved to both Shang and Shen that their skills were equal. The deadly duel did not stop until Juliette stabbed herself in the shoulder, as she could not gain the attention of either combat through shouting. Ashamed of himself, Shen Kuei comforted Juliette and gave a knife to Shang, telling him he had earned the right to kill him. Shang refused and left for London.

Shen Kuei's relationship with Juliette saw some strain as he returned to the Chinese government, which prompted her to break up with him due to the major difference in their political views. Shen would eventually break away from the service of any government after his brother was killed due to Shen's involvement in the espionage arena, and Juliette and Shen eventually reconciled and are as far as anyone knows, still together. To make a living, Shen currently pursues the career of a freelance mercenary with an unmarred record of success in battle, with only a few draws to Shang Chi to draw attention away from his successes. Shen Kuei has tangled with other characters from the Marvel U. including Spider-Man, Wolverine, and most famously Deadpool, who he defeated. Deadpool now admires Shen "The Cat" Kuei as a God amongst killers, as do many mercenaries, secret agents, and assassins around the world.