0 - unplayable in 40 card singleton
1 - effectively unplayable
2 - has low tier constructed decks it might go in
3 - has mid tier constructed decks it does go in
4 - pretty powerful stuff with several potential homes, able to perform well in lower powered cubes
5 - powerful stuff that is either just too narrow or has too many superior alternatives
6 - fringe cube worthy
7 - cube worthy
8 - cube staple
9 - unpowered cube bomb
10 - powered cube bomb
Githzerai Monk 6.5
The power is low and the cost is higher than I would like but this is a bit of a Time Walk in a lot of cube situations these days. This can push through for a big alpha strike as the final part of a nice curve or from a long drawn out stalemate. It can equally buy you that key turn as the control player when under pressure. I don't feel like I want a five mana 3/2 flier in aggro, midrange, or control, however it seems like it will perform well in all of them. I think it will struggle to get play due to that low power trapped in a high cost card but if it can then strong performance might well let this innocuous break into the mainstream.
Contraband Livestock 2
I actually kind of like this card. Much as I typically hate the randomness of the dice roll cards on a removal spell as clean as this it simply adds a nice dynamic as to calculating when it is a good call using it and indeed on what. You might well need to aim it at one of your own things and hope to make a 4/4 which is cute. Sadly I don't think this has enough raw power to get there. Removal has come along a very long way indeed. A few years ago we were all Declaration in Stone and Valorous Stance this would have had enough power to compete. Alas now it looks pretty laughable in the face of Prismatic Ending, March, Solitude, Winds of Abandon, On Thin Ice even. It is basically an Over cost Pongify but in the best removal colour rather than the worst.
Wrathful Red Dragon 6
Too polar sadly. Against red and green decks this is an absolute beating of a card. Against the Esper colours however it is eating spot removal and losing tempo. Average performance of this is probably fine for most cubes but you really want cube cards to be more even in performance than this if you are aiming at the best quality of games.
Ancient Copper Dragon 2
I do love treasure but without haste or some protection this is not the kind of six drop you can afford to run in cube. With the right support this can get rather more interesting. The average mana generation per hit is over 10 which is going to allows for some stupidly big turns. One hit effcts like Sneak Attack and Shallow Grave seem like the best way to try and use this card at which point why are you not just playing Eldrazi? What is this middleman adding?
Storm King's Thunder 1
Fun but way over priced. Copying stuff is best done on the cheap rather than having the ability to scale. This is the kind of card you need to have a huge pile of treasure to go mental with!
Intellect Devourer 4
A bit of a Gonti sidegrade, and ultimately a downgrade. The main perk here is getting to have a 3 for 1 rather than the 2 for 1 Gonti offers. Sadly it is much worse all round as the body you get is less useful and the card you get is far far less useful. You also do not gain any information over your opponent which sounds minor but I would argue is a significant part of Gonti's power. You critically give them a decent window to kill Devourer and get their card back most of the time as well which turns your 3 for 1 into a 1 for 1 and removes the only upside this had over Gonti. I think the low impact of this card given how far up the curve it is will ruin the performance. Sometimes it will absolutely own the game but a lot of the time it will do relatively little. It is also the kind of card that you can play around when you know it is a threat which all but kills the ceiling on the card.
Hammers of Moradin 4
Comically close to good in 1v1 for a card with myriad. This is just a little costly and vanilla for the effect but it is a powerful high tempo means of pressuring an opponent. A tapper and an attacker in the same card is right up white weenies street, they can just do a bit better for raw power, options, or consistency when it comes to three drops.
Ancient Silver Dragon 1
Comically this card has an ability that is actually a drawback in 40 card decks. This literally has a quicker clock for decking yourself than it does for killing them... Pretty awkward. Fun, and powerful, but random, and dangerous, and all sorts of narrow.
Explore the Underdark 3
Despite the cost this will feature in gate decks due to both the ramp and tutoring and be pretty impressive in those decks. Too slow elsewhere.
Earthquake Dragon 2
For when you really want to go all in on the board! You have to have nearly 10 mana of dragons already in play before this looks like good value for mana at which point a Wrath is bending you over so hard. Recursion is cute but like, how often is it going to be a thing given how unwieldy this thing is to begin with? Much more likely playable due to the high CMC for use with the likes of Nourishing Shoal than it is to play as intended.
Fraying Line 1
Cute flavour card but really just a (too) slow Wrath.
Mighty Servant of Leuk-o 6
It should be relatively easy to crew this with two dorks in cube as you can over crew and still get the draw. Crew 4 is a lot though. It means this will be offline some to a lot of the time. That is probably OK as it is pretty hard not to get value out of this. With 1 hit you are drawing 2 cards and if they try and kill it with removal then it is a two for one. This is cheap and threatening and tough to answer. If you can expect to crew it then it is going to be scary. I am not sure how many decks that is and how often they will want a card that isn't brimming with consistency. This looks to have enough power but might lack the appeal. Looking forward to testing it.