if he gets to andrew before you do , he has passed through you and taken some of that power back , sarias followers are on that plane probably using the power now to destroy the demons who have come through the gateway , if he passes through them or calls upon their power to boost his own , he will have enough to claim andrew and then he will go after your children , enslaving them will not be enough for him , he wont be able to control them fast enough to satisfy his blood lust , especially jacob .