Dark fantasy

From Guidevines

A sub-genre of fantasy and horror, referring to works containing elements of both. In the absence of a clear line dividing all fantasy that is not also horror from all horror that is not also fantasy, a given work is likely to be classed by some readers as being in one genre, but not the other, while other readers will class the same work in both. For example, some readers may regard Stephen Donaldson's Chronicles of Thomas Covenant as being solely a work of fantasy, not horror, while others will call it dark fantasy (because they will see elements of horror in it as well as elements of fantasy). Similarly, some readers may regard H.P. Lovecraft's Cthulhu Mythos as being solely horror, not fantasy, while others will call it dark fantasy (because they will see elements of fantasy in it as well as elements of horror).

A related term, dark horror, appears much less often (based on Web searches). This tends to refer to works, particularly visual works, that emphasize gruesome subject matter.