"His eye dwelt with insatiable avidity upon the beauteous orb. A sensation till then unknown filled his heart with a mixture of anxiety and delight: a raging fire shot through every limb; the blood boiled in his veins, and a thousand wild wishes bewildered his imagination" (pg. 68) (metaphor)
This passage contains a number of literary devices, but central is the "raging fire" in Ambrosio's veins. This fire represents sexual desire, which, like fire, can offer sustaining warmth or can cause terrible burns.
"Her habit's long sleeve would have swept along the chords of the instrument: to prevent this inconvenience, she had drawn it above her elbow, and by this means an arm was discovered formed in the most perfect symmetry, the delicacy of whose skin might have contended with snow in whiteness" (pg. 80) (metaphor)
As Matilda plays her harp by Ambrosio's sickbed, she draws up her clothing and exposes more of her body than Ambrosio has ever seen before. He compares her skin to white snow, emphasizing her beauty as well as her purity - which may be dangerously deceptive.
"'In what have I been imprudent, Father? I have sacrificed a pebble, and saved a diamond: my death preserves a life valuable to the world, and more dear to me than my own'" (pg. 92) (metaphor)
Matilda reveals that she is dying of poison - and that the poison that is killing her is the serpent venom she sucked from Ambrosio's wound. Though she saved Ambrosio, she has condemned herself to death. She lies on her deathbed luminous with joy, however, because her sacrifice has saved her beloved Ambrosio; she likens him to a valuable diamond and herself to a worthless pebble. This conveys her esteem for Ambrosio, which also flatters his ego even more.
"They had felt the sharpest darts in misfortune's quiver; those which remained appeared blunt in comparison" (pg. 428) (metaphor)
After the difficult events narrated in the novel, Raymond, Agnes, Lorenzo, and Virginia go on to live happy lives, as this quote describes. Misfortunes are compared to darts due to the pain they cause, and the protagonists have endured such terrible difficulties that anything less seems negligible in comparison.
"If you are not more cruel than wolves or tigers, take pity on my suffering" (pg. 387) (metaphor)
After the discovery of her pregnancy, Agnes is imprisoned in a tiny room in the crypts and given only bread and water to drink. Trapped in darkness, her only company is the nuns who are occasionally sent to torment her about her terrible sins. When she hears Raymond coming down the stairs, she cries out to her, beseeching her to take pity on her suffering.
Like predatory wild animals, these nuns have no sense of mercy and no pity. But in some ways the nuns are even crueler than wolves and tigers; these animals kill their victims quickly, whereas Agnes has been kept alive and her torments prolonged.
