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
Skyway Robber 7
This is a side-grade on Ethereal Forager with a lower floor and a higher ceiling. This is always four mana to get into play making it a much slower and lower tempo card. Further to that if played without escape it is a straight up Phantom Monster. Without support you have to do that first and have it die and not get exiled or something. Robber really wants to get looted away so as to skip Phantom Monster phase. So, those are some significant downgrades on Ethereal Forager, let us look at some upsides. Escape means this is coming back, it is value and threat just as Phantom Monster with recursion. That alone obviously is not wildly improving the power but it does give it those angles that a top end late game card want, that bit more threat. Phoenix of Ash is a scary card to play against as it is eventually going to get you unless you properly deal with it. Obviously Phoenix is way more aggressive and in a colour better suited to applying pressure but Skyway Robber remains an ongoing concern and a useful tool for any deck looking to eventually win. Next big perk of Robber compared to Forager is that Robber will cast the spell for you thus enabling pretty big tempo swings. If you can connect with a Temporal Manipulation under the Robber then that should end the game pretty hard! Further to that you get an extra card and the ability to play artifacts. The latter is useful and helps increase the playability a healthy amount. The former is likely a con and not a pro. If you escape 5 useful cards and connect 5 times you probably won a couple of turns ago. More likely is if you exile 5 useful cards Robber is answered and those cards are gone and do not come back the next time you escape Robber. In reality you are likely best off escaping with a good artifact/instant/sorcery and one or two weaker ones so that you do not put all your eggs in one basket. Sadly we must return to some cons again. You need to connect to get your card and your card must be played right away ruining the ability to control the game with counter magic. That is all probably for the best. Ethereal Forager is a brutal cube card and pretty high tier. A calmer version such as this Skyway Robber is going to play better. Robber seems rounded enough to see play. It scales nicely and offers quite a range of ways you can put it to use, some threat and some value and some pro active board presence. Blue does already have a good amount of cards that want to make use of the bin; Dig, Cruise, Murktide, Uro, Demilich, and of course Forager itself. Not to mention things like Snapcaster and little Jace that want some targets left in the bin to use themselves. You cannot go too ham on such cards in a deck, and therefor in a cube design as well. This will up the bar a little for Robber but I still do expect it to last. Demilich is generally a bit more awkward and narrow. Skyway Robber will either take its place at worst or coexist alongside it.
Change of Plans 0
Far too narrow and expensive for what is offered. A messy meld of combat trick, card quality, and dork protection, all things you want a lot cheaper than this.
Cephalid Facetaker 3
Cute card but needing of specific support to reach the needed power level. In cube there are much more in the way of EtB triggers than there are on combat damage triggers making this a card that will perform worse than the more conventional Clone cards. The ability to pro-actively make this onto a board without clone targets helps it but not enough to make it actually good.
Interesting card but near impossible to rely on and abuse.
Aerial Extortionist 7
At worst this is a 4/3 flying Dissipate for five. That is a reasonable tempo play with acceptable threat levels. Should the Extortionist survive it is going to start ruining opposing boards while gaining loads of value and/or tempo as it does so. The card is a little clunky, a bit too middle of the road to excite a control player and a bit top end for the aggressor. Despite being really rather the midrange card it is pretty all round playable and has a decent chance of working out in the cube. Probably not quite as good as Angel of Sanctions but very close and a less risky means of disruption. Often I find with Sanctions that I deploy it and stand to lose if they answer it which this will not suffer in the same way.
Tivit, Seller of Secrets 6
Very cool but too much value and not enough end the game right away. Getting two treasure back immediately does allow you to protect your six mana sorcery speed play with counter magic but getting to six mana to deploy this in the first place isn't super easy, especially not with 2 mana counters left to use. I tend to like threats that come down a little sooner and help me survive. This is certainly good enough on power levels thanks to the EtB trigger but it is just a bit 3 colour and six mana to see enough play. Perhaps if Esper returns to the go to control archetype rather than 2 colour builds as it seems to be presently.
Boss's Chauffeur 0
Some reasonable top end but this simply has way too high a chance of entering play as a laughably small dork, or getting bounced or exiled or otherwise easily negated. No evasion and needs support both kill this cards chances by themselves. Together they have got me wondering why I am bothering to review this card.
Grand Crescendo 6
This is somewhat two cards in one. It is a poor rate Secure the Wastes but it is also just a WW spell to counter removal, mass or spot in most cases. Secure the Wastes currently has a cube slot but it is a pretty tenuous one. I am not sure this will supplant it. Secure is already mana inefficient in terms of tempo. Secure is taking a trade off on tempo for versatility. Cards tend to be a product of their parts and so the most well rounded cards are a nice balance of their parts so to speak. If you push Secure further down the line of modes at the cost of more mana inefficiency you are polarizing the card. Say it was 5 rated for tempo and 5 rated for versatility then the card is worth 25 total. If you trade of 1 in tempo to gain 1 in versatility you have a 4 and a 6 giving you a 24 total. Bit of a scenic route to say I think Cresendo is too weak in the options it provides for those options to excite. The card is fine and playable but I cannot see it improving a cube.
Indulge // Excess 2
My sort of card and certainly one I shall make room for in some fruity build one day. Sadly not the sort of thing one can enjoy in a cube setting without suffering win percentage losses. Both halves are narrow and while they support each other to some degree you are then ramping at five mana. If you can get a big attack through a pile of treasure probably isn't the go to payoff when typically competing with killing them.
Seize the Spotlight 0
A long way from the power needed when you just have the one opponent.
Crash the Party 0
Just a win more card and not a very good one at that. Play a threat when you are playing a six mana card. Avoid things than can do literally nothing.
Scepter of Celebration 5
This is a lot of mana for a Rancor but that trigger can get out of hand fast. It is pretty hard to contain after the first hit as well as there will be more tokens to equip up and swing with. A 3/1 trample isn't something you can ignore and if you are trying to contain it with tokens you are just letting them make more. Much as this seems fairly powerful and threatening it is also slow, clunky, and not really a card that does something by itself. Green certainly has room for that kind of card more than other colours, it has mana to spend on things like this, and often small spare dorks it would like to turn into relevant cards. I shall have to give this a test despite instinct being a no. It is the lack of speed that harms this for me, it is a high mana threat with reach but it is taking control of a game very slowly and not doing loads to disrupt the opponents plans in that time. Scepter risks doing nothing without other dorks and it risks costing you a lot of mana on re-equipping it too frequently. When put up against a card like Creeperhulk there really isn't much of a case for Scepter.
False Floor 0
This is stupidly hard to use. If you have no dorks you are getting hit one more time and this does nothing but kill vigilance dorks... If you have dorks and are able to apply pressure you have to attack into their board before you can fire off your on-board one-sided Wrath which will typically allow them to create a board state where you no longer want to Wrath. There is just no good way to use this card in a sensible way in 1v1 without a card like Turnabout at which point why are you even bothering?