The Babylonian Brotherhood, referred simply as the Order, was a precursor to the Assassin Brotherhood which operated from Babylonia. Through Iltani, one of their most prominent members, they were responsible for the assassination of the Macedonian king Alexander the Great.
The Order was a secret Babylonian organization that dealt in assassinations of those they deemed tyrannical. In the 4th century BCE, they counted a woman named Iltani among its members.
Although Babylonia had by then ceased to be a sovereign entity, the Order was still active when western Asia fell to the Macedonian Empire of Alexander the Great. Iltani set out to assassinate Alexander during his campaign in what is now modern-day Afghanistan, but she was forced to withdraw when she found him too well-guarded in the citadel of Herat. As a result, she turned to an alchemist of the former Achaemenid Empire who provided her with a deadly but slow-acting poison. In 323 BCE,, Iltani succeeded in killing Alexander with the poison and retrieved his Staff of Eden that had been entrusted to him by proto-Templars.
For its parallels with the later Assassin Brotherhood, the Order later came to be seen by the Assassins as one of their antecedents and dubbed the Babylonian Brotherhood, with Iltani being honored posthumously as one of their legendary predecessors.