Definition of Motif
The Castle of Otranto is split up by lots of narrow passageways and hallways, and descriptions of these recur as motifs from the beginning of the book until the end. In Chapter 1, when Isabella escapes from Manfred's sexual advances, she decides she will use a secret passage in the twisting underbelly of the castle as her exit:
In this resolution, she seized a lamp, that burned at the foot of the staircase, and hurried towards the secret passage. The lower part of the castle was hollowed into several intricate cloisters; and it was not easy for one, under so much anxiety, to find the door that opened into the cavern [...] that long labyrinth of darkness.
Horace Walpole uses the motif of portable lights at several points in The Castle of Otranto to signal the incomplete, confusing or partial understanding of something by a character. For example, in Chapter 1 when Manfred is trying to prevent Isabella from escaping the Castle, Walpole writes:
Unlock with LitCharts A+The noise of the falling door had been heard by Manfred, who, directed by the sound, hastened thither, attended by his servants with torches. “It must be Isabella,” cried Manfred, before he entered the vault; “she is escaping by the subterraneous passage, but she cannot have got far.” What was the astonishment of the prince, when, instead of Isabella, the light of the torches discovered to him the young peasant, whom he thought confined under the fatal helmet!
The natural world of The Castle of Otranto is as tumultuous as the events going on inside the castle's walls, and Walpole uses the motif of a thunderstorm at three important points in the book to illustrate this. For example, in Chapter 5, a mighty vision of Alfonso appears to announce the true heir to Otranto, and this vision is accompanied by thunder:
Unlock with LitCharts A+[...] a clap of thunder, at that instant, shook the castle to its foundations; the earth rocked, and the clank of more than mortal armour was heard behind. [...] The moment Theodore appeared, the walls of the castle behind Manfred were thrown down with a mighty force, and the form of Alfonso, dilated to an immense magnitude, appeared in the centre of the ruins. “Behold in Theodore the true heir of Alfonso!” said the vision: and having pronounced these words, accompanied by a clap of thunder, it ascended solemnly towards Heaven [...]