In Chapter 1, Laura makes an allusion to the biblical story of the Tower of Babel when describing the nature of her household growing up:
[Mademoiselle De Lafontaine] spoke French and German, Madame Perrodon French and broken English, to which my father and I added English, which, partly to prevent its becoming a lost language among us, and partly from patriotic motives, we spoke every day. The consequence was a Babel, at which strangers used to laugh, and which I shall make no attempt to reproduce in this narrative.
Babel refers to the Tower of Babel, a tale in the biblical Book of Genesis that explains the origin of different languages spoken across the world. According to the story, people spoke a single language and sought to build a tower to reach the heavens. However, God was displeased with their ambition and caused them to speak different languages, leading to confusion and an inability to understand one another.
Rather than explaining the presence of multiple languages in Laura's household in simple terms, Le Fanu makes an allusion to present this information in an evocative, memorable way. By using the term "Babel," Le Fanu refers to a situation of confusion caused by the presence of multiple languages spoken at once, much like the confusion that arose after the Tower of Babel incident in the Bible. Laura's description conveys a sense of chaos, and the allusion elevates that chaos to biblical proportions for the reader.
An allusion to Cleopatra occurs in Chapter 3 when Laura describes the room in which Carmilla stays when she first arrives at the estate, and the allusion also serves as foreshadowing:
Our visitor lay in one of the handsomest rooms in the schloss. It was, perhaps, a little stately. There was a somber piece of tapestry opposite the foot of the bed, representing Cleopatra with the asps to her bosom; and other solemn classic scenes were displayed, a little faded, upon the other walls. But there was a gold carving, and rich and varied color enough in the other decorations of the room, to more than redeem the gloom of the old tapestry.
Laura describes a tapestry featuring Cleopatra, the Queen of Egypt who ruled from 51 to 30 B.C.E. Cleopatra was the last ruler of the Ptolemaic Kingdom. The imagery in the tapestry alludes to the famous account of her death. According to legend, Cleopatra committed suicide by allowing herself to be bitten by an asp, a type of venomous snake, as a way to escape capture and potential humiliation by her enemies.
The reference to the asp's bite in the tapestry is an instance of foreshadowing that hints at Carmilla's identity as a vampire (since vampires also bite people) as well as the tragic events to follow. Moreover, the tapestry contributes to the room's gloomy and sinister atmosphere. The choice to depict such a grim and tragic scene adds a sense of solemnity and darkness to the scene.