Free A Jungle of Stars (1976) by Jack L. Chalker

there was little need to do anything. Bound to this planet, Hunter was neutralized.
    "But, about a hundred and fifty of your years ago, The Hunter discovered that the ancient destruction wrought upon Earth by the Kreb had left severe weaknesses in the space-time fabric; and, using one such, he was able to transcend the ancient curse that bound him here and to go out again to the stars. He built his headquarters here, and brought real space travel back to Earth from outside. Killed on Earth, he is doomed to remain here, body after body, life after life. But killed in Haven, he is able to overcome the ancient Kreb barriers and be reborn elsewhere. Once loose, his megalomania knows no bounds, his abilities for chaos are unchecked. To save the Next Race and all future races, The Bromgrev organized and began this war: to hold the key positions, to control the key sectors, to protect the Next Race until it could develop to a point where it can do to The Hunter what his own race was unwilling or unable to do."
    "All very interesting, but not very important to me. Certainly it doesn't make much difference, from my point of view."
    "There is a crystal world," the creature continued, as if it had not been interrupted, "whose sentient life forms live for more than a million years; where time, and even thought, is that much slower relative to our own.
    Should hosts of The Hunter and The Bromgrev die at the same instant, in normal space, and if one knew of the impending death and the other did not, it would be possible for the one who knew to control the confused one who did not, to guide him to that crystal world, and there trap both in those near-immortal bodies. The war would end; the Next Race would develop normally and deal with them both, and millions of lives would be saved."
    Savage was quick to catch the implications. "That means put the both of them together, and an executioner," he pointed out. "So The Bromgrev is coming here, after all. But you picked the wrong boy, Bakkus or whatever your name is. Once bought, I stay bought."
    "Our agents reported the rather violent death of one Joseph Santori on a military installation. We made the assumption that you had killed him," the thing said.
    "No comment," Savage replied with a smile. "How can you blackmail a dead man?" "Blackmail has nothing to do with it," explained the agent of The Bromgrev. "Our people routinely check out new recruits to your side. We made the connection and decided, after much thought, that you were one of our best candidates. The key is revenge, Mr. Savage. You are a vengeful person. Your hate is deep inside, ready to explode. You killed Santori when he did not attempt to kill you except in defense. Rage, Mr. Savage. You killed a surrogate because your true murderer eluded you."
    "McNally," Savage whispered. It was a tone that was almost inhuman.
    "Ralph Thomas Bumgartner," replied the creature. "One of the best professional assassins around, and, like yourself, an immortal in the pay of The Hunter. You can never revenge yourself upon him, for neither of you could ever really damage the other. We could tell you where he is, but it would do you little good, you see."
    "Tell me anyway," Savage commanded eagerly. "I want to know."
    "Oh, I will. . . for it will verify my story. But you do not want him any more than you really wanted poor Santori. It is his employer you should seek, the one who arranged for you to die in a manner so bizarre that you would never truly suspect the premeditation of your murder. The one who had to know pretty closely the moment of your death so that you could be intercepted, in the proper emotional state, and subjected to the correct theatrics, so that you would do as was preordained by your murderer for you to do.
    "I speak of your employer: Stephen Wade, The Hunter."
    Savage sighed. "I'm ahead of you on that one," he told the creature. "I just didn't like to think about it."
    "Bumgartner -- McNally -- has a cottage on an island