According to the Encyclopedia Britannica an allusion, in literature, an implied or indirect reference to a person, event, or thing or to a part of another text. Most allusions are based on the assumption that there is a body of knowledge that is shared by the author and the reader and that therefore the reader will understand the author’s referent.
On page 94, Pieces says: "Oh Frankenstein, be not equitable to every other and trample upon me alone, to whom thy justice, and even thy clemency and affection, is most due. Remember that I am thy creature; I ought to be thy Adam, but I am rather the fallen angel.". This is one of the most clear allusions in the novel. Pieces is clearly showing himself to be Adam, trying to gain Frankenstein's sympathy.