And if you know your personal shadow, you can shut all the doors."
Marie-Louise von Franz - A Matter of the Heart

So you can say the personal shadow is the bridge to the collective shadow or the open door to the collective shadow. But the collective shadow comes up in those terrible mass psychoses. It’s like if you have your room, and there is one door not shut, and there the devil can come in.

That was their personal shadow. But then they joined in with the Nazi movement for that reason and did much worse things than they would have done normally under normal social conditions.

First you have this area, of dim, dark side, and behind it lurks the other.
I’ve for instance, seen that, when Germany went to the devil in Nazism, people fell into it through their personal shadow. For instance, they didn’t want to lose their job because they were clinging to money.

In the Christian tradition, it would be the devil. And that has always been personified and felt as something which has not to do with, directly with the human being. I mean, if somebody is possessed by the devil, he is much worse than just, he is not human. It’s demonic.

If one is jealous or if one is suddenly possessed by wanting money or soon, one could know about it if one is honest with oneself. But the collective shadow has to do with the dark side of the archetype of the Self, that means, is the shadow of the God image.

To put it bluntly, it is that part of life which they have always shirked, probably by means of a pious lie. That sows the most virulent germs."

C. G. Jung - Collected Works Volume 17 - Development of Personality, par. 87

This statement would be rather too perfunctory and superficial if we did not add by way of qualification: that part of their lives which might have been lived had not certain somewhat threadbare excuses prevented the parents from doing so.

This is tantamount to a general law. When one projects the darkness, then at some point it comes back, and the victor is easily
dehumanized..."

Marie-Louise von Franz - Archetypal Dimensions of the Psyche

Just as in the case Graecia capta victorem cepit (Greece, defeated, conquers the victor), again and again in history the defeated have psychically conquered the victors.