Hmmm. I'll answer in a vague way due to plot spoilers, but I'll also clear up your question I think. 

Firstly, the characters will encounter a Guardian in the very beginning of the RP. Suffice it to say, they will gain these powers from this Guardian which is why I used the word "inherit". The reason for their need? Well, that's complex because as I was telling Aria, every character will have their personal reasons to do this. As for a narrative reason, it is because the cult they are a part of believe that the world cannot truly be at peace under the fear that these god-like beings will once again storm the globe in an all out offensive. Of course the cult has no proof that these beings exist either.... Until the beginning of the RP that is. 

Once they discover that the Guardians are indeed real and powerful beings, they aspire to rid the world of them because they believe they would be saving humanity by doing so. Of course, this is also a twisted truth of sorts and there's many more details than just that, but that's the surface of it. I like to title my RPs after the essence of the game and the name "Veritas" definitely will hold meaning in the grand scheme of things. 

I hope I answered well enough. I was trying to navigate between plot details that shouldn't be revealed in the OOC as of yet haha.