In a departure from many Cthulhu Mythos stories, Lumley's characters are not helpless victims of unimaginable forces which can drive humans mad by merely manifesting themselves.
Instead, Titus Crow, his friend Henri-Laurent de Marigny, and other Lumley characters confront Cthulhu's minions in a series of increasingly large-scale encounters, in which humans, although outmatched, try to fight back.
In a letter to the journal Crypt of Cthulhu, Lumley wrote: Crow has been known to survive any number of encounters with monsters, although he may not always be able to defeat the creatures.
In an interview with Lumley, Robert M. Price suggests various possible models for Crow, including Miro Hetzel, Jack Vance's futuristic detective, Doctor Who, Mervyn Peake's Titus Groan, August Derleth's Dr. Laban Shrewsbury, William Hope Hodgson's Carnacki and Seabury Quinn's Jules de Grandin.
Lumley doesn't acknowledge any of these as conscious inspirations, saying that Crow's time-clock (which derives from Lovecraft's "Through the Gates of the Silver Key") long predates Who; that he's never read Peake's Gormenghast and that the similarity of names is coincidental; and that he "was never too keen on" Derleth's Shrewsbury.