Shada D'ukal was first introduced in Timothy Zahn's Heir To The Empire trilogy, but only as a very minor character, a bodyguard of a smuggler named Mazzic. In the Specter Of The Past/Vision Of The Future duo, however, Zahn fleshes out her character and background considerably, becoming a rather major part of these two books.
She was born on the planet Emberlene, which had been decimated many years earlier in a massive space and ground attack. Life was very harsh, and death and disease and hunger were a given. An organisation called the Mistryl shadow guards, an elite group of exquisitely trained warrior women, commissioned personally by the Eleven Elders of the People hired their services out to the oppressed and powerless of the galaxy, in return for money to keep Emberlene alive. Shada joined the Mistryl when she was young, where she became a highly trained covert agent, doing the Mistryl's bidding on countless planets. On Tatooine she helped the Rebellion get the technical readout for a prototype component on the Death Star's superlaser. Several years later the Eleven planted her with the smuggler Mazzic, as a bodyguard, believing his group to grow to be one of the largest in the galaxy. It was not to be, however, and Shada was with him for twelve years, before her service to the Mistryl came to end on Borcora over her belief that the Mistryl were no longer the honourable organisation she had joined so many years ago.
Shada decided to join the New Republic, but ended up going with Talon Karrde in search of Jorj Car'das, a former smuggler who Karrde believed would have a copy of the Camaas Document, which contained the names and clans of the Bothans who sabotaged Camaas' planetary shield generators, who were the focus of a civil war which was threatening to tear the New Republic apart. As it turns out, he didn't have it, but Shada learnt the truth behind Emberlene's destruction and Karrde gained some valuable information which directly led to the downfall of Moff Disra and Major Tierce, and the signing of the peace treaty between the New Republic and the Empire.
Shada became a member of Karrde's intelligence service, replacing Mara Jade. This intelligence service was a neutral organisation that provided information to both the Empire and New Republic about the goings-on in the galaxy.