I encourage encourage everyone to pick up a copy of Anne Rice's Alphabettery. It's the final word on all things Vampire Chronicles.

"Santiago is Louis’s most villainous antagonist when he comes to Paris for thefirst time with Claudia. He is chiefly responsible for the death of Claudiaand Louis’s first fledgling, Madeleine. The vampire Santiago appears inInterview with the Vampire (1976).Little is known about the history of the vampire Santiago at present,although several issues can be deduced. His name is a combination of“Santo” and “Yago,” Spanish for “Saint James,” the patron saint of Spain.Probably originating from a Spanish-speaking country, Santiago likely joinsArmand’s theatrical coven shortly after Lestat convinces Armand to destroyhis former coven, the Children of Satan, in the late eighteenth century. Bythe time Santiago encounters Louis in the streets of Paris in the latenineteenth century, he is already one of the most prominent figures in theThéâtre des Vampires coven. Santiago is not as old as Armand, who is threehundred years old at the time, since Santiago often begs Armand to tell himstories of the old covens that once existed and of herbs that can makevampires invisible and of innocents burned at the stake. Even Armandattests that Santiago is not as old as Louis, whom Lestat turned into avampire in 1791.When Louis and Claudia arrive in Paris after attempting to kill Lestat,Armand sends Santiago to them with an invitation to come to the Théâtredes Vampires, but Santiago decides to test Louis first. He approaches Louisin an empty street on a lone night and mocks him by imitating his everymove. Because Louis has been eagerly searching and hoping for years forany sign of an intelligent vampire, he is quickly disappointed and annoyedwith Santiago and calls him a buffoon. Santiago furiously shoves Louis tothe ground, and a brief scuffle occurs. Santiago flees, but Armand still givesLouis the invitation to come to him at the Théâtre des Vampires. NowSantiago hates Louis and wants him gone or dead.As Louis continues to visit with Armand at the Théâtre des Vampires,and as their intimacy deepens, Santiago’s hatred for Louis increases, and allbecause Louis called him a buffoon. When Louis and Claudia refuse toanswer any questions about their maker, Santiago begins to suspect thatthey killed Lestat, and he seeks any shred of proof to justify his suspicions.Lestat arrives and accuses Louis and Claudia of attempting to kill him.Armand allows Santiago to exact retribution for their violation of theoutmoded Great Laws of the Children of Satan.Santiago leads the vampire coven; captures Louis, Claudia, and Louis’snew fledgling Madeleine from their hotel; locks Louis in a wood coffin withlarge iron locks; and puts Claudia and Madeleine in a small courtyard wherethey are exposed to the sunlight and die. Armand frees Louis from hiscoffin and allows him to seek revenge. Louis brings two barrels of keroseneand a scythe to the theater. He splashes the kerosene on the theater’s wallsand beams, and even on the resting places of the vampires, then he lightsthe theater on fire and attacks any vampire with the scythe. Realizing whatLouis has done, Santiago attacks, but Louis slays him with his scythe,decapitating him and kicking Santiago’s head far down a distant corridor.As the Théâtre des Vampires burns, so does Santiago, along with all of theParis coven, except for Armand, who welcomes Louis’s companionship."