Ks

When Kiriel first journeys to earth, he wants a vacation. Pretty soon, he figures he could do something more with his time. Why take a vacation when you can permanently alter the universe? Perhaps he'd just settle for impacting a few lives.

Or, the way he sees it: "I bet I could manage it, too—just leave a couple of small marks, nothing that would hurt anyone, nothing that would interrupt the space-time continuum. Just a few teensy asterisks that would linger after I was gone, the way a boy deep in the woods carves an initial in a tree trunk that no one will ever see: KIRIEL WAS HERE" (15.17).

So, he comes up with the idea of leaving Ks behind. These are symbols of the change that he's had on people in Shaun's live. For example, he encourages Reed to stop bullying people, or tries to get Lane to see how beautiful she really is. Kiriel even gets Jason to agree to make some friends. By far the biggest impact he has is on Shaun, even though he never meets the guy. He gives Shaun a second chance at life. Literally.

Kiriel's Ks might seem small to us, but they mean a lot to him. He's sick of just watching people torment themselves while he does nothing. His Ks are a sign of the work he does in people's lives, and they're a sign of his contribution to something bigger, too, to helping create instead of just reflecting people back to themselves.