Rob Halliday

Question: It is implied that Satan and the forces of evil are always watching out for Damien so that when anybody gets anywhere near to hurting him they invariably meet a very sticky end. So how is it that, at the end of the film, Kate Reynolds is able to stab Damien to death with such apparent ease when all previous efforts to kill him have failed so dismally?

Rob Halliday

Answer: Damien states at one point that as the birth of the Nazarene gets closer, his strength fades accordingly. Presumably this also applies to any forces assisting him.