The Keeper of the Matrix was a Time Lord. Councillor Volstrom consulted with him to discuss the Matrix, which had been suffering from disturbances that the Keeper recorded on infostamps. (AUDIO: Songs of Love)
According to one account, Engin was made Keeper by the Sixth and Eighth Doctors following the High Council's overthrow in the wake of the Ravolox scandal (PROSE: The Eight Doctors) and was still in the position during the Last Great Time War. (COMIC: Sky Jacks)