Traitor Spy Trilogy

Sonea, former street urchin, now a Black Magician, is horrified when her son, Lorkin, volunteers to assist Dannyl in his new role as Guild Ambassador to Sachaka, a land still ruled by cruel black magicians. When word comes that Lorkin has gone missing Sonea is desperate to find him, but if she leaves the city she will be exiled forever, and besides, her old friend Cery needs her help. Most of his family has been murdered - the latest in a long line of assassinations to plague the leading Thieves. There has always been rivalry, but for the last decade the Thieves have been waging a deadly underworld war, and now it appears they have been doing so with magical assistance...