Composer

The Composer is a Forerunner or possibly one of their machines that can turn a living being into a Monitor or ancilla, it could also be used to extract ones memories and turn them into a geas as it did with the Lord of Admirals. There are few details as to what the Composer really is, such as whether it is either a Forerunner or a machine. Even it's uses are merely guessed upon, since it's has no solid description throughout Halo: Primordium, including a lack of description of its apparance.