The Eighth Deadly Sin (Nanatsu no Taizai fanfic)

All over Britannia, word of the infamous Seven Deadly Sins spreads like wildfire. They were seven deadly criminals who bore the mark of vicious animals on their body. Their crimes corresponded to a deadly sin that man should try not to commit: Pride, Wrath, Lust, Greed, Sloth, Gluttony and Envy. But, what man would not know, was that there wasn't always seven criminals, and that there definitely wasn't just seven deadly sins. The was one more. One more deadly sin, one more deadly criminal. Yet something happened, which lead to him being forgotten by the masses, and lead to the exclusion of him from the band of criminals. How could man forget that the sin itself was deadly? Because it was a sin that man committed too often in daily life.
Deceit.
Deceit was too common in the world of man. Lies, trickery, conning. How was it that it got forgotten as a deadly sin? Who was the criminal that bore the mark of an animal, and shouldered the sin of deceit upon himself...?

Disclaimer: I do not own anything from the Nanatsu no Taizai world! I only own the main character and any other characters that pop up.

THIS FANFIC WILL INCLUDE SPOILERS FOR THE MAIN STORY!! IT IS ADVISABLE THAT YOU WATCH THE ANIME/READ THE MANGA BEFORE READING THIS FANFIC!