Brother to Shadows — Andre Norton

DEBT OF HONOR, OATH OF BLOOD

Since early childhood, Jofre has honored the ways of the Brotherhood. Now the illustrious order of bodyguards and assassins has cast him out in disgrace, cruelly condemning the young Shadow to wander a treacherous world alone. But his true destiny awaits him in a stinking port where the vilest of star-traveling scum congregate. For here he is bound by blood-oath to a gentle reptilian knowledge-seeker on a quest to penetrate the mysteries of time itself--a sacred duty imperiled by those who would use a window on the past to wreak havoc upon an already volatile universe. In war and revolution--on far planets and in shattered lands--Jofre's skills and spirit will be tested in fire and in blood...as his sworn mission is threatened by a mysterious Shadow-sister whose own secret agenda could doom them all.