What is "grimdark"

a. (context fandom English) Having a gloomy, dystopian atmosphere.

Grimdark is a subgenre or a way to describe the tone, style or setting of speculative fiction (especially fantasy) that is, depending on the definition used, markedly dystopian or amoral, or particularly violent or realistic. The word was inspired by the tagline of the tabletop strategy game Warhammer 40,000: "In the grim darkness of the far future, there is only war."