Following the death of Luis de Santángel, the Brotherhood was left without eyes inside the Spanish Royal court. Concerned about the unmonitored activities of Queen Isabella I and her history with the Templars, a group of Assassins journeyed from Rome to Spain in an attempt to infiltrate the Queen's inner circle.

After arriving in Barcelona, the Assassins visited Santángel's quarters in the hopes of collecting any remaining intelligence on their enemies. Although the Templars had ransacked his chambers, the Assassins discovered what the Templars could not: a journal hidden in a hollowed-out wall. It revealed that Santángel was slowly poisoning the Queen with the help of a servant woman working for Isabella.

The Assassins studied their royal target and confirmed her strong ties to the Templars and Cesare Borgia. The Assassins decided to finish what Santángel had begun. They found his accomplice and convinced the hesitant servant to continue poisoning Isabella until her eventual death.