Simon R. Green: Deathstalker War [1997] paperback

Owen Deathstalker, the last of his line, was wrongly outlawed by the evil Empress Lionstone IV, but in making an enemy of Deathstalker, the Iron Bitch sowed the bitter seeds of rebellion. Now that rebellion has fomented into war. Opening skirmishes on Mistworld and Haceldama and Virimonde reveal just a few of the horrors the Iron Bitch is prepared to unleash on the rebels, but the opposition only fuels their determination to win justice. It’s war: no quarter, no prisoners, no compromise.