Manfred's worst action is, perhaps, his desire to marry the fiancé of his dead son, the double figure for his daughter. His fate at the end of the novel is just as bizarre as his prior behavior. The reader is constantly reassured that Manfred is usually quite rational, but is never given any evidence of this; even his actions at the close of the novel do not quite follow logically—Manfred becomes a monk in a convent. The combination of the ineffectuality of both the "good" and "bad" figures results in a tone closer to the absurd than the terrifying. 
	Possibly the most recognizable Gothic trait is the presence of a (physical or psychological) castle. The architecture of the gothic era, as Walpole understood it, was previously disparaged as a primitive distortion of roman architecture, he himself had become quite enamoured with the style and sought extensively to recreate it in his own home.  The castle takes on such a presence that it becomes in essence a character in its own right. The castle is used, in a basic literary sense, as an aspect of the oppressive, preternatural atmosphere and as a tool in creating the terror that propels the plot forward.  It usually serves to entrap the "victim" character and thus provide tension and act as an austere authority present in a novel whose villains and victims are even less stable than the castle's conveniently crumbling foundations. This state of decay also parallels Walpole's general opinion on the state of the world at the time he was writing The Castle of Otranto. The castle succeeded in taking on almost a life of its own in the novel, becoming almost a protagonist in its own right. The castle itself foils Manfred's plots, is the deciding factor in the mysterious medieval prophecy, as only the castle could determine if someone was "too large to inhabit it" (17). In a comical, for today's audience, twist the phrase "grown too large" is taken quite literally in the story, a giant suit of armor appears in snapshots at many points in the novel, first the outsized helmet falling (in the castle) onto Conrad, then the glimpse of the leg and the giant sword carried by a hundred soldiers. On just the third page of the novel's text a helmet “an hundred times more large than any casque ever made for human being, and shaded with a proportionable quantity of black feathers” crushes Conrad, Manfred's only son (19).  The use of the armor as an antagonist provides yet another counter to the heroic image of the 'chivalrous knight'. The connection to the almost sentient presence of the castle (and other inanimate objects, most notably the coughing painting and the mysterious suit of armor) and the superstition of the medieval past is clear, and Walpole adapts it to his new genre through the use of the novel format, and the psychoanalysis it allows the writer to engage in (which he studiously avoids fleshing out). 