Doomskar 8.5
This might be better than Wrath of God although it's fate is a little tied up with how many other foretell cards are in the cube that you might play alongside a Wrath like the card draw or counterspell options. If there is little to no chance a foretold card from a player isn't a Wrath you can play accordingly. If it can be anything then it is a whole lot harder to know how to act. So why is this Wrath so good? Well, it can Wrath on turn three. Or four. It is the first five mana Wrath that solves the issue of possibly being dead before you can use it and that makes it great. Not only can you use it early when needed, you can also split up the cost so that you can keep up counter magic or deploy something relevant on the same turn as the Wrath. All very juicy. It might be better than Wrath, not by much, and if it isn't better it will still be plenty good enough for cubes. Certainly preferable to Shatter the Sky!
Brinebarrow Intruder 2
A side-grade on Zulaport Duelist. Will have some uses as a good supporting one drop with some nice redundancy but hardly a powerful or frequently sought after card.
Orvar, the All-Form 4
What a funny Hill Giant this is. More of a Dodecapod all told. This is powerful anti discard but I am not sure how good the heroic style ability is. There are not many things you cast on your own stuff in cube, certainly not in blue. Sure, it is nice to be able to Shock dorks into existence but you need to have all those things. That is situational and only upgrading a card rather than generating extra value. You need combat tricks and that sort of thing to really get loads out of this. Still, reeks of combo potential. Eternal Witness and Mutagenic Growth is kind of a combo, a build your own Hatred affair with a load of free 2/1s into the mix. This seems rather too polar in performance to be a great cube card. Hill Giant floor is not a good look. Constructed seems to have a lot more interest in things this exotic dork. One to keep any eye firmly on.
Wolverine Riders 2
A mini Verdant Force but with much nicer tribes and a bit of life gain. Elves love to amass a lot of bodies and there are not loads of great ways to do that. This is quite powerful and quite useful but I fear it is just far too far up the curve for the effect. Elves can be winning on the spot with top end cards leaving good value supporting top end lacking in uses so I am not sure where you run this. It isn't exactly broken enough to be Skyshroud Poacher worthy. It isn't quite busted enough just to run outside of tribal.
Starnheim Courser 2
This is a lot of card for a common. The double type cost reduction is an eye opener for sure. The issue here is that it is a body you are unlikely to want in whatever deck you want the cost reduction for. It is vulnerable and a little higher up the curve than ideal for a fragile cost reducer. Alela decks seem like the most likely to want something like this as the potential synergy overlap is decent.
Great Hall of Starnheim 3
If this could be used at instant speed it would be rather the impressive card. It is pretty strong as it is, compare it to Tomb of Urami for example! Still just a little narrow and fair for cube use but certainly notable for efficiency and power. Just a nice way to pad out a deck with a low curve or limited mana sinks.
Valor of the Worthy 2
They are going to make some playable auras soon! They are getting closer and closer. There are only a couple of issues with this card as it compares pretty well to other one mana threats. This has scaling and tempo perks with some built in removal protection as upside. The issues here are being in need of a thing to play this on and thus not being as proactive as you might like for an aggressive one mana card. The other is simply power. Yes, this is better than most one drops but not by much and one drops are not exactly powerful. Stop them being turn one plays or potentially even plays at all and those inconveniences and risks more than outweigh the small perks. While I like this in theory for white weenie decks I don't much like it for existing aura archetypes, a 1/1 flier token later is not at all what they are looking for. All told that means this card probably never sees play despite looking interesting and decent.
King Narfi's Betrayal 2
Somewhere between a Divination, a Gonti, and a Grapple with the Past. This is mostly just a value tool and a fairly slow one but it has bonus support and disruptive capabilities. It is also noteworthy that opponents cards are typically well suited to your needs for the matchup. This can't find you lands, forces your hand into playing things, and can even wiff. The small upsides don't make up for these somewhat disastrous failings. You can't even find your 4th land with this. Powerful but mostly ill suited.
"Rune of" cycle 1
I can't see much use for the black or white runes but the red, green and blue have some mild application being that they do rather help some of the more commonly used equipment. Trample really improves Swords and Jitte as does flying. Sadly there isn't really the tools to support the combination of your Runes and equipment in those colours. In a white deck I could see it but in others you will mostly just have equipment without runes or runes without equipment. Ill advised for such a small upside. The Rune of Speed is interesting as it lets you build your own Lightning Greaves (thanks Shuko). Sadly I can't see how that is useful when you can just play Lightning Greaves or one of the many other red ways to haste things up while jumping through less hoops.
Depart the Realm 3
Strict upgrade to Disperse. Sadly I can't see this packing enough upside when we compare to Brazen Borrower, Cyclonic Rift, or even just Into the Roil/Blink of an Eye. The only small chance for this is due to how good foretell looks in Azorious control with counterspells and wraths on the table. Unlikely to be enough to push this past the bar but a cute and playable little spell none the less.
Bind the Monster 4
Great answer to mana dorks. Not a great answer to much else. This hurts a little too much against threats, fails to stop EtB, passive, or activated abilities without tap costs. It can be removed too resulting in the return of the dork to active duty. Certainly this is a playable card that will have homes being so cheap and so well suited to some specific tasks. What it probably will not be is playable in draft cube where you need power and reliability on your cards.
Elven Bow 1
Lovely flavour and feel but just not powerful enough. I don't want a 2/3 reach dork for 3. The left over piece of equipment isn't strong either. It goes a little way to protecting green in the air but it is just so expensive to use. Solving a weakness is all well and good but you need to not offer a massive power reduction to do so. Solving issues is a perk for already powerful cards not a thing that makes a card good by itself.
Icebreaker Kraken 2
Cool card. Missing a few parts to be great such as trample and tapping down things as well as keeping them that way. Even with those you still need to be playing this in snow decks, You want this costing less than 8, ideally 6 and that is only really happening if all your lands are snow. For drafting cube that makes this a mono card and thus not good enough. I can see this locking out some late games and winning with repeat casts and lots of stuff that puts land back into play. Nice to have a bit of a late game payoff for snow decks too. A reasonable fair card but designed such that it feels like it has some uses.