Jason does a great job covering all your spoiler needs for Dragons of Tarkir, but we have some late-breaking spoilers today that I wanted to write a little about. They're big, they're scary, they're... rocks.
But really cool rocks.
All of these Dragon monuments function the same way: they add one of two colors to your mana pool, and for six mana of the appropriate colors they can become a 4/4 Dragon (you can find all five here).
So the question is: are they playable? Obviously when we ask this question we're talking about Limited, and I think these pass the test. We haven't seen a ton of success from people playing Cluestones or Banners in the past, but I think the payoff here is much better. Not only do I get a mana rock that ramps me to my big dragons, but for six mana I can get a Dragon at instant speed whenever I need it! That's a lot more payoff than sinking mana into it to draw a card, and I think these will make the cut in the new draft format. I doubt they're a super-high, but you have to be happier about playing these than a Banner.