Potentially, she could cost as little as 5 mana if you have all 8 card types in the graveyard (Artifact, Creature, Enchantment, Instant, Land, Planeswalker, Sorcery, and Tribal. However, Tribal was only a thing in Lorwyn, Morningtide, and Rise of the Eldrazi, plus one Tribal card for Rebels in Future Sight. So she will only cost as little as 6 in Standard. However, in Modern, since All is Dust is playable, you could potentially have all eight. Also, like the infamous Tarmogoyf, she counts card types, so if a card has multiple card types, she counts each of them.
So, a 13/13 with flying, trample, and protection from instants seems like quite a bargain, especially since you'll pretty much never cast her for the full 13 colorless mana. But the Promised End does something particularly spectacular. When you cast her, you gain control of target opponent during that player's next turn. Essentially, you get a Mindslaver effect. In Modern, that is one of Tron's main win conditions. This effect is great, and is similar to the original Emrakul's ability to take an extra turn. But there is a drawback. Your opponent, if that opponent survives that is, gets to take an extra turn, too. Then again, it's pretty hard to deal with a 13/13 flyer.
The cast trigger makes Emrakul, the Promised End a creature that you really have to think about when you cast her. In many situations, you'll be able to just end the game. You just need to be sure that giving that player that extra turn won't cost you. Still, there's a lot to love about this new Emrakul and she'll definitely see play in Standard, if not Modern, and elsewhere. I'm curious to see how she fares in Commander, as the original Emrakul is banned. I could see her doing damage pretty much anywhere that she goes. Also, consider that if she comes to play but isn't cast, you don't have to worry about her ability. There's a lot to think about when brewing with the Promised End.
If that ability wasn't already good, Ulrich, Uncontested Alpha gets to fight a target non-Werewolf creature you don't control every time he transforms. Being a 6/6, this is going to take out just about anything. There's a lot of value here. On top of that, even though Ulrich is legendary, you can technically have one Ulrich of the Krallenhorde and one Ulrich, Uncontested Alpha on the board at once, as long as they don't ever "see" each other when they are flipped to the same side. As good as Ulrich looks, in regular Constructed play, being a 5-mana Legendary Creature is going to mean you can't play the full 4 copies. In Commander, Ulrich should be extremely powerful. Finally, Werewolf Tribal has a strong leader.
One of the best ways to deal with Eldrazi in Standard is Stasis Snare, which can exile the creature at instant speed. But with Coax from the Blind Eternities, you can simply get that Eldrazi back to your hand. This feels good. It could either see a good amount of play, or none at all. Tutoring up an Eldrazi, or any Tribal Eldrazi card for that matter, seems well worth 3 mana. Many Eldrazi decks already play blue mana so it doesn't seem like much of a stretch to include this. Whether it ends up in the mainboard of some Top 8 deck or simply as a sideboard option will determine its eventual value.
So far, Eldritch Moon is off to a strong start. Obviously, the best cards are usually going to be spoiled first. But as Shadows Over Innistrad was already a big hit, and blocks only have two sets now instead of three, there should be a lot of value packed into this concluding sequel to the new Innistrad block.