The Starspawn were made at the heights of the Fourth Intergalactic Empire, as Imperial assassins. It was a construct, a robotic f'ire-and-forget' assassin programmed to track down it's target, kill it, and then self-destruct. It was highly intelligent, able to follow the most twisted of trails to find the target. One day, one of the Starspawn decided it didn't want to kill the target. This was totally unacceptable to the Imperial programmers and they came up with an elegant solution. They separated the stalker from the assassin. Now they had a highly intelligent construct that, as the stalker, could track down the target and, when it was found, the assassin, an emotionless, murderous killer, took over. Then the Starspawn self-destructed as planned. They were pleased, and the Starspawn worked as planned for hundreds of years.
But everything decays, including Intergalactic Empires. The Fourth broke up into treason, betrayal and regicide. The Emperor fled into the depths of space, and the victorious Ministers who created the new Empire sent a Starspawn after him. It, too, worked as planned. It found the Emperor, and the assassin took over. When the deed was done and the Emperor lay breathing his last, the assassin retreated into the shadows, and the stalker looked at what had been done. He had killed his God!
At that moment, the elegant programming that had split his mind disintegrated. He Had Killed His God! Stalker and Assassin both knew the awful, unbearable truth, and the truth nearly destroyed them both. Much of his peripheral data was lost, the navigational data, the historical data, but he still knew who they were. But his God had given him one last command. As the Emperor breathed his last, he said, “Kill them all.”
The Starspawn sat for untold times, pondering the message.
Kill them all. But who? All living things? That couldn't be, for his God had been living.
He had been sent to kill his God by those who wanted to kill. That must be it. He had been told to kill all those who wanted to kill. He would succeed. Since his navigational data had been reduced to meaningless garbage, he simply picked a star ahead of him and engaged the drive.
It's primary ability is it's Time Mastery, which affect his attack, his movement and his defenses.
Its claws, while not very powerful, have almost no way to be defended against. Armor and other defenses are simply bypassed. It's victims look like they have been slashed to death by hundreds of sharp but not very deep razor cuts. It will cut up a lot of heros, but takes a lot of cuts to be fatal.
It's Timeslip is a teleport that can only go where it could have traveled to by normal means, such as walking. It is, to our senses, instantaneous. It can be traced by opened or smashed down doors and such but it is hard to corner him.
It's Timesiphon is it's ability to siphon off three-fourths of all attacks against it into alternate realities. Likewise, all missile weapons, including lasers and bullets, have a 75% chance of also vanishing into an alternate reality. Originally, when it was meant to go against one target, then self-destruct, it didn't matter but now that he takes on repeated targets, there is always a chance of being slammed by an attack that was already over, or hadn't happened yet. That is best handled by GM decision to give the heros a breathing space during a fight as the Starspawn suddenly takes off to recover from the 'phantom' attack.
It locates it's target by telepathy, scanning to identify the capacity to kill that is his reason to kill. It can regenerate, healing itself slowly. It has about twice the reaction time of a human, which means that it can make two attacks to a human's one. Still not enough to handle a whole group of heros, but it helps.
Its greatest vulnerability, other than simply being dogpiled by a bunch of heros, is through its own conscience. If it can be brought to wonder if simply having the capacity to kill is not what his God meant, he will back off, defending himself only while he thinks this through. If heros can roleplay this, they may be able to stop him without killing him.