The Remembering Machines were twelve men and women who were resurrected, in a similar, although far more advanced way to the stalkers of the Nomadic Empires. The main difference is that these were not machines of war, but history recorders, built to remember all that had gone before. The Remembering Machines were built by the mysterious Pyramid Builders. They were hidden in a temple "so far north you started going south again" with workshops attached where the priest-engineers would take one of their number and turn them into a Remembering Machine. Whenever a chief or chiefess died, their body was converted into a remembering machine, so they could tell future generations about their wisdom and experiences.
The Stalker Fang's brain was taken from one of these workshops in the days of the Green Storm. The temple was destroyed by the Green Storm after the brain was taken in fear that the traction cities would discover it and use its secrets against them. The remembering machines would have presumably been destroyed in the blast.
Shrike is a remembering machine, as his brain was taken from the temple by a snowmad and sold to Nicola Quercus. After Kit Solent died, the ancient stalker brain was put into his head. At the end of A Darkling Plain, Shrike tells the villagers that he is a remembering machine, and that he remembers the days of traction cities and Tom Natsworthy and Hester Shaw.