You know this old irish superstition/myth to fix perfectionism in knitting? When you knit something you leave a piece of your soul in your work, so to avoid that you leave little mistakes in it so your soul can escape.
Now imagine Michael knowing damn well what is going to happen, that they will be killed, possibly destroyed. So he thinks of this myth (because come on, it's supernatural, everything can be a thing here) and creates, he creates but nothing is perfect, always little mistakes slipping in. He tries it with Adam's soul, tries to put it into his works so at least Adam will be save, protected and will go undetected. It never works, so many works discarded and so much frustration and fear building up. He loses Adam, he loses the one thing he tried so hard to keep and protect and goes a little insane. He destroys all his failed creations and sits with his destruction for minutes, hours, days. So in one last hope of comfort he takes the remnants of his failures and begins his final creation. He never notices the perfection, not a single mistake to be found. He gets killed, torn apart, reduced to nothing but a little piece hidden deep within layers of protection in this last creation.
Adam gets to live, revived by Jack, but he is struggling. No warmth, no comfort, no connection, nothing to connect to. He's lonely, starving for something, someone who isn't there, someone who won't return.
He walks and searches. He doesn't know what he's searching for, but eventually, he finds it. A tiny little object, easily mistaken for something of less value. It calls to him, makes him feel safe and protected, a tiny spark of something familiar. He keeps it, for it feels like it belongs to him and to him only. He cherishes it, protects it, would kill for it, but he just doesn't understand what it means. Until one day he loses sight of it for one tiny moment, he doesn't even realise what's happening. It falls and breaks and shatters into a thousand pieces. They lie scattered across the whole room, impossible to fix or even find them all. It breaks Adam's heart and he doesn't understand why but he panics, picks up the broken pieces that cut him and leave his hands bloody. He sits in the middle of the destruction, staring at the pieces, staring at his hands, staring at the mess that was once a perfect creation, before he let it get taken away and allowed it to be destroyed. He is numb and needs to lie down, close his eyes before he loses his mind. His hands tingle, he doesn't notice through his grief and doesn't see the way the cuts seem to heal on their own.
He opens his eyes when there is a gentle hand on his cheek, wiping away tears he didn't feel escaping his tired eyes. Another hand holding his healed ones, chasing away the numbness that spread in his body and mind. A warmth washes over him and he finally feels whole again. No more coldness, no more fear, no more grief, no more yearning for his missing piece.