I’ll give you a hint: all the errors are in the first sentence.
If the name of the collection/group/whatever is the Seven Deadly Sins, why would you capitalize only part of that name? *shakes head* Also, I think that any story in which the Seven Deadly Sins are characters, Hell ought to be treated as proper-noun name. (Perhaps Humanity ought to be capitalized, too, for that old-fashioned feel… and because it refers to humans, collectively, and not to the quality/condition we call humanity — the state of being human or behaving in a way we believe is appropriate for humans.)
Every hundred years, the Seven Deadly Sins meet in Hell for a tournament. The winner earns the right to be humanity’s most prominent sin until the next tournament comes around.