From my personal collection, this trilogy penned by Raymond Feist & Janny Wurts is set in Kelewan, the world on the other side of the spatial rift that featured in the Riftwar Saga.  Lady Mara, the titular 'Daughter of the Empire' must contend with ambitious warlords, dark magicians and deadly assassins to preserve the Empire.
1 'Daughter of the Empire' - 1991 printing, 421pp, very good condition
2 'Servant of the Empire' - 1991 printing, 691pp, very good condition
3 'Mistress of the Empire' - 1993 printing, 676pp, very good condition