Matilda Grimwald (AKA Tilly) is a Sartorian taxi driver who lives and works in a slum district of Milgramcyad, the capital city of Mondias, during the time of the Great Invasion. She has a cheerful demeanour and a generous nature.  She is physically strong and streetwise.  A chance encounter with Sheraleen Conder (later Mulvaney, then Donovan) led to the two of them becoming good friends.