A Tone Shift that seeks to make a work of fiction more gritty and cynical. An effective use of this tone shift could mean that archetypes which we are accustomed to see acting in a more noble setting will have to act in one where they must think and act grimly in order to make progress, thus forcing re-examination of the tropes involved, or the use of new tropes and expansion of the setting, utilizing different sorts of characters and stories. In practice, however, writers can be too lazy to realize all that potential and end up simply "spicing up" a work with gratuitous gore, cursing, and sex to make it more "adult" — often overdoing it in the process. This is not to be confused with Tough Love.
When done right, Darker and Edgier works are a case of Tropes Are Tools. When a show uses this trope as a tagline, you can expect a mixture of: awful things happening to the characters, twisted backstories giving them a reason to angst, protagonists becoming less heroic, and the setting becoming much bleaker. However, this all works IF it's done right.
