Timeliner Trilogy Series by Richard C. Meredith

FROM FAR IN THE FUTURE COMES A HIDEOUS WARNING OF DESTRUCTION.But the message is not clear, and the result is a mad scramble to change the present—all possible presents—in order to avoid the future. For the recipients of the message are not humans but Kriths, lizardlike beings from a parallel Timeline.Using machines that move sideways in time, a band of dedicated mercenaries and Krith leaders cut a wide swath through countless Timelines... moreFROM FAR IN THE FUTURE COMES A HIDEOUS WARNING OF DESTRUCTION.But the message is not clear, and the result is a mad scramble to change the present—all possible presents—in order to avoid the future. For the recipients of the message are not humans but Kriths, lizardlike beings from a parallel Timeline.Using machines that move sideways in time, a band of dedicated mercenaries and Krith leaders cut a wide swath through countless Timelines. It is a brutal and bloody struggle that has no end—until one of their strongest fighters begins to ask questions the Kriths would rather not answer. less

From the year 7093 ... 4000 A.D. ... Greetings. We have waited until the last possible moment to send this back to you. But we know that we can wait no longer. We are all doomed. While there is still time let us tell you what has happened to us all.There is a civilization of beings on the far side of the galaxy. They are totally alien, inimical to all that is human and Krith... moreFrom the year 7093 ... 4000 A.D. ... Greetings. We have waited until the last possible moment to send this back to you. But we know that we can wait no longer. We are all doomed. While there is still time let us tell you what has happened to us all.There is a civilization of beings on the far side of the galaxy. They are totally alien, inimical to all that is human and Krith. They have been biding their time, aware of us, building a great armada of interstellar warships to com and destroy us all.Why they hate us so we do not know, nor do we know how to fight them. Humanity and Krith stand alone against the alien hordes coming to destroy us. And we are all but defenseless against their weapons.All the works of our great mutual civilization shall perish unless ... less

ALIENS HAVE MEDDLED WITH TIME, CREATING COUNTLESS PARALLEL WORLDS IN THE PROCESS.But as Eric Mathers desperately skudds through a dazzling array of Timelines, they crumble around him. The prophecy of a catastrophe in the far future is coming true now!Eric's survival depends on two things. He must follow the directions of a phantom force known only as the Shadowy Man. And he must travel to a parallel Earth in search of a true time machine... moreALIENS HAVE MEDDLED WITH TIME, CREATING COUNTLESS PARALLEL WORLDS IN THE PROCESS.But as Eric Mathers desperately skudds through a dazzling array of Timelines, they crumble around him. The prophecy of a catastrophe in the far future is coming true now!Eric's survival depends on two things. He must follow the directions of a phantom force known only as the Shadowy Man. And he must travel to a parallel Earth in search of a true time machine. But to obtain it Eric becomes the general of an army—of his own clones. And that is only the beginning... less

At the Narrow Passage; No Brother, No Friend & Vestiges of Time