Some story questions

[mansarde]

1:
A quote from Agrippa:

Weyer was a brave man and dared to proceed where I did not. He unearthed a number of cavern temples and gathered a whole collection of Orbs.
But unlike every other finder since the fall of the Mithraic faith, he was able to unshackle the horror you and I connect with the Orbs.
He used them and was able to travel far and wide. Beyond the world itself.

I guess you don't NEED multiple orbs to travel to another world, but the more orbs you have, the more power you have.
And opening portals to other worlds seems to be only ONE of its many possible uses. Maybe different orbs grant different powers?

2:
Another quote from Agrippa:

Not many orbs are left. They sometimes consume themselves or break when used by an uninitiated.
I was lucky. The Orb I found spared my life and returned to where I had found it.

This implies that the orbs react differently to different wielders. Maybe most people don't have the mental capacity to deal with the orbs side effects, whereas others (as Agrippa) were barely getting away with their life.
It seems if you have a prepared and strong mind and know what you're doing, you can even manage multiple orbs.
I guess the closest comparison I can come up with is that of nitroglycerin:
It's highly unstable and must be handled with care. If you don't know your way around it, then it can blow up in your face. But if you know all about its dangers, its physical attributes and reactions, etc. then you have a powerful weapon.

3:
Too lazy to research this one at the moment.

4:
I think the tortures and kills fulfilled both purposes.
They had to be tortured in the most horrible way with as much terror beforehand as possible so as to have their blood enriched by "vitae", which enables Alexander to live longer (and in turn have more time to find orbs and try to use them for his "lifelong" goal).
And the ritual deaths were indeed necessary to keep the shadow at bay. It's like throwing meat at a wild animal to keep it from eating you.
And as long as you feed it new meat... you'll live a little bit longer.