I like how you worded the ability. It really seems to fit the verse. It's also rare to have a covenant or curse that actually can be useful as either an art OR an enhancement, but this one definitely could.
I think it may be too powerful though. Cards that can be active outside battle and end a battle/extend a battle are very powerful, but if this card was an artifact, I don't think I'd have a problem with it. My concern is that it gives Brown an additional CBN battlewinner.
Now, I recognize that Gomer/Uzzah/Amelekite's Slave cannot use it, so it doesn't help the meta defense. But I fear that it may create a new meta defense, since this card is kind of like a hybrid between Unholy Writ and Haman's Plot (in terms of functionality).
I applaud your effort to make the card match the verse. I think it just needs a little toning down (not sure how that would be done) in order to be balanced enough.