Granting creatures flash had no benefit, since they're already on the battlefield. What you want is a separate line that says "As long as ~ is in your graveyard, you may cast creature cards as though they has flash."
That said, this is incredibly overpowered. Getting this into your graveyard is a very easy condition to fulfill without ever having to cast it, giving you a better anthem than white, the anthem color, ever gets, and potentially for free.
This card seems hella overpowered. All you need is an early discard outlet, and if your opponent doesn't have a way to exile cards in the graveyard you basically instantly win the game.
Looks odd for a card to have protection from red, when red is one of black's allies. It'd be much more intuitive for this to be with prot red, or with prot green.
I'm no legacy player, but this is now the best card ever to play with Force of Will.
Granting creatures flash had no benefit, since they're already on the battlefield. What you want is a separate line that says "As long as ~ is in your graveyard, you may cast creature cards as though they has flash."
That said, this is incredibly overpowered. Getting this into your graveyard is a very easy condition to fulfill without ever having to cast it, giving you a better anthem than white, the anthem color, ever gets, and potentially for free.
This card seems hella overpowered. All you need is an early discard outlet, and if your opponent doesn't have a way to exile cards in the graveyard you basically instantly win the game.
Looks odd for a
card to have protection from red, when red is one of black's allies. It'd be much more intuitive for this to be 
with prot red, or 
with prot green.
In many ways this is still more powerful than the 5-color Maelstrom Nexus, but it's at least now at a more feasible level than it was before.
I was going to make a comment very similar to Alex's. I might suggest that it add a clause about only spells you cast from your hand having cascade.