Mashup of Crumbling Sanctuary and Sacred Scripture.

I tried several other combinations. It would be a lot more interesting if it was a global effect, and you could build your deck to deny your opponent the advantage of it. But that would probably just change the game too much. So, I stuck with the basic combination of effects: mill that many + cast one.

And I put it on a sphinx so people will like it :) It ended up very similar to cards like Wrexial, the Risen Deep but that's probably ok.

Maybe I should make a defensive-oriented one as well?

I think the version that keeps the game moving is better in a game-design sense than the version that discourages attacks and so leads to stalls. This is a pretty awesome card.

It's extremely powerful though. Consider that this repeatedly gets the effect that Jace's Mindseeker does as a oneoff. At the moment this is even cheaper than the Mindseeker too; I suspect this would get pushed up to 7 mana even at mythic.

Yeah, the risk of a defensive one is that it just nerfs attacks; what I want is one where attacks turn into super-awesome feedback loops of people playing more and more powerful spells and attacking faster and faster until they win by milling. But obviously, that's at odds with "play a deck designed that your opponent can't take advantage of it".

Agree on cost, but I won't bother to tweak it until I have a good idea what it should be.

It's gonna be hard to cost it - I'd be happy to run this as the capstone on an infinite mana combo, if I had to.

It's game winning mill and ridiculous silliness combined. What's not to like?