Originally a dead man, the Shrike has been re-animated and brought back to life.
You could hardly call it life, as he is more machine than man and programmed to follow his orders.
But does he?
A key part of of the Shrike's journey is discovering his true identity which was lost to him.
As his story progresses he hunts for one of the protagonists of the series (and crucially his adopted daughter), Hester Shaw which requires him to go on a murderous rampage to get to her.
Through a convoluted plot point, Shrike acts as a bounty hunter with a kind of self defense mechanism of not harming children. In the book of Mortal Engines, he is conflicted with his mission given him by Magnus Chrome, the Mayor of London. The Shrike is ordered to kill Hester and in return, she will be re-animated like himself so they may live together. He however does not want Hester to die, and gives her every chance to live.
Kit Solent is his real name and that represents the time he had a wife and children.