In the time it's taken for the remaining Gammas to properly react and begin attacking, Childermass has stepped back into the shadows. He's gone one second, back the next, but only to burst up from a Gamma's shadow and grab them, meaning to pull them through when he vanishes again.

Lacking anywhere better to send them, his goal is to blindly jettison them from Polaris altogether. Outside, wherever outside is, so long as it has a shadow to cling to when he does it.