The Reign of the Brown Magician (Three World Triology/Watt-Evans, Vol 3)

Pel Brown is transformed into Pelbrun the Brown Magician after passing through a mystic portal into magical, highly advanced lands, and when he loses his wife and daughter to murder, he eases his pain by using the matrix of magic to overturn the laws of mortality. Original.

ER LIFE AND DEATH
They called him Pelbrun the Brown Magician. He'd been plain old marketing consultant Pel Brown until the day a mystic doorway had appeared in his basement. That improbable portal had led him and his family to the magic land of Faerie; another had opened the way to the super-science universe of the Galactic Empire.
But this was no fairy tale . . .
At first Pel had sought the key that would take them safely home. But before he could wrest the matrix of magic away from the despot Shadow, Pel's wife and daughter were brutally murdered. Neither absolute control over the matrix nor rulership of Faerie could ease the pain in Pels heart--until he realized that the matrix held power over life and death!
So this once-ordinary man set out to overturn the irrefutable laws of mortality. But even his newfound omnipotence couldn't protect him from the pitfalls that lay ahead, as both the Empire and Earth's military sought to exploit his incredible power. Then the Empire i