Yes, yes, I know prophets are already strong. Hush for a minute.
A lot of the Old Testament is prophecy. Some of this is relaying God's word to his people (which is, strictly speaking, the definition of a prophet), while some is predictive in nature. I'll be focusing on the latter category here.
There are already a few takes on this kind of prophecy in the game - Birth Foretold comes to mind. However, since so much of the Bible (the OT especially) is prophecies, perhaps a completely new take is required.
My suggestion is this: Prophecy is a new identifier. The card itself will be a territory class enhancement, with two separate parts of its ability - a weaker first half, and a powerful second half. In the identifier, after Prophecy, the "fulfill condition" will be in parenthesis (akin to Taunt). Before the condition is fulfilled, the (weak) first part of the ability will be active; after the condition is met, the (strong) second part will activate. All prophecies have the implied identifier "Limit one per territory".
For an example, let's use Isaiah 53, twelve verses of prophecy about Jesus. The most famous verse - and the one I'll use here - is verse 5: "But He was pierced through for our transgressions, He was crushed for our iniquities; The chastening for our well-being fell upon Him, And by His scourging we are healed." (NASB). Since this is a reference to Christ, the fulfill condition will be "Son of God is played". Even before Christ came, this was taken as referencing the Messiah, and was a message of hope, so the initial ability (the first half) will be something along the lines of, "When your hero loses a battle, you may reveal an opponent's hand." Certainly not useless, but not necessarily game-breaking either. However, after SoG is played, it will gain a much more powerful ability: "You may remove a good dominant from your discard pile to heal and make all evil characters vulnerable to all heroes." While still not game-breaking (by the limited number of uses), this is now a much more powerful card.
Here's the result:
Now, a lot of the OT prophecies are about Jesus. In fact, one of my concerns about this are actually that playing SoG will, with enough of these types of cards, set off a ridiculous chain of ubercharged abilities. One way to avoid this is to focus on other parts of Jesus' ministry (for example, Isaiah 35:5 "Then the eyes of the blind will be opened and the ears of the deaf will be unstopped." could have a condition related to blindness being removed, or an enhancement about Jesus healing blind/deafness). Still, there are other prophecies that don't involve Christ. For example, we could go to Jacob's prophecy concerning his sons:
You could even get evil in on the fun. One great example of a (true) evil prophecy would be Balaam's prophecies (okay, so maybe they actually blessed Israel, but Dreaming Pharaoh is evil too
):
So? What do you think?