Would one use ab or ex in the following?

[Darklander]

Would one use ab or ex in the following?
Da mihi potestatem defendendi locum ex/ab magia externa spatii.
Grant me the power of defending a place from outside magic of space.

 

[Dantius]

I believe "ab".

 

[Bitmap]

It should be ab

I think "defendi loci" would be a bit better. (Off the top of my head I can't say if "locum defendi" is wrong, though)

By "space" do you mean "outer space" as in "the universe"? In that case, I think "spatii" doesn't work - you would be better off using something like "universi"
If by "magic of space" you mean magic that would change a place from a rectangular room to a circular one, "spatii" is right

btw. "da mihi potestatem" is roughly translated as "give me the power" in the sense of "give me the opportunity to do something" or "allow me to do something". What you're trying to translate sounds like a magical spell - if that's the case, I'm not sure potestas is the right word to use

 

[Darklander]

It is a magic spell from Mage: The Awakening. As for Space I mean area the definition of space regarding area or place.
As for Da mihi potestatem; I have had no other objections to its usage from anyone else in the context of a magical spell.

 

[Bitmap]

It is a magic spell from Mage: The Awakening. As for Space I mean area the definition of space regarding area or place.

In that case stick with "spatii"

As for Da mihi potestatem; I have had no other objections to its usage from anyone else in the context of a magical spell.

I don't really think it is fitting ... potestas means "power", but more like the power you have as somebody's master/ruler or as an authority

Metonymically, it can also be "power to do something" in the sense of "opportunity to do something" or "permission to do something", but that's not what I think of when I think about the power you obtain from a magical spell.

I like vis because I have read it in the context of divine power or the power of nature and other abstract phenomena, so I think it would also fit with a magical context.

I won't prohibit you from using potestas, of course.

You can just exchange "vim" with "potestatem" (and vice versa) without having to make any change to the rest of the sentence