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
Wand of Wonder 0
Low returns in 1v1 play, both down to being restricted to one hit and by the fact that instants and sorceries are typically both the cheapest and the most situational cards in cube. Comically you are probably better off running a Jayemdae Tome - not something that can be said of much...
Elder Brain 0
This is lacking in too many ways. It is basically just a value tool on a mediocre body. There is no real tempo to be had with this, it doesn't really offer disruption directly. It isn't even all that threatening. For seven mana I want a whole lot more, I want an EtB trigger or something. This is too vulnerable and unreliable at doing much more than being a 6/6.
Ancient Brass Dragon 0
Ancient Brass Dragon manages to be all round better than Elder Brain and yet still fail at every single hurdle. For cube this needs haste and then trample or a mana discount as well! Perhaps all three buffs.
Minsc & Boo, Timeless Heroes 9
We go from a pile of unplayble cards to this clear bomb. The Timeless Heroes are oppressively good to the point they will ruin games a lot like Oko does. I can see this getting banned in my unpowered cube pretty quick. Even in a world with Fury and Tef3 and Omnath and all those mad cards I think this will be oppressive. As this isn't something you can play in modern or standard it will only be oppressive in cube. Indeed that is how it is able to be so pushed, it cannot do too much damage in EDH, legacy or vintage and isn't legal elsewhere. Cube is the only place it will be oppressive. So what is so oppressive? Well, lets take Questing Beast, Ophiomancer, Bloodbraid Elf, and some random generically good planeswalker and jam all those things together without scrimping on the power level and you get Minsc and Boo. It is high tempo, high options, high threat, and high value. It literally ticks all the boxes. You need to kill Minsc as quickly as possible else it is game over and that is easier said than done when it can start out at four loyalty and has a blocker that can be a 4/4. Mostly Boo will not be blocking, Boo will be smashing face so while you scramble to deal with Minsc you will just be dying to Boo. I normally consider a planeswalker good if three activations generally means the game is over, well in this instance it literally is, Minsc and Boo kill quicker than most threats out there. This is easily good enough with just the passive and the +1 but just in case we needed more there is the -2 which gives move value, more options, more control, and a nice powerful way to break open any sort of board stall. You won't need the -2 often because of the power of the rest of the card but it is certainly no slouch. There is only really one tiny chink in the armour of this card and that is the ability to respond. Three and one point damage effects that you can either respond to the EtB trigger or loyalty abilities with do allow you to handle the card without getting utterly smeared in the process. I guess you can counter it too...
Firkraag, Cunning Instigator 0
Very cool in multiplayer and very hard to make more than a 3/3 flying haste in 1v1 play.
Captain N'ghathrod 1.5
A cool option for tribal horror payoff but this is a little conditional and a little high up the curve to be having all that much impact. Horrors are barely a tribe now and will remain so when this dude comes out.
Faldorn, Dread Wolf Herald 6
A powerful self contained card that offers good value while also being a solid board development tool. Faldorn also has strong synergy with any sort of discard and graveyard stuff and scales up nicely with most red card draw effects such as Light up the Stage. While this is a very powerful card it is slow, a little vulnerable, and gold. All minor but enough that I don't have much interest in adding it to my cube. Certainly more than powerful enough to hold its own in cubes.
Nalia de'Arnise 2.5
A great all rounder for a party deck offering ongoing value to begin with and a good means to finish a game off once you attain a full party. Likely something I would consider for a tribal cleric deck as well given the exciting synergy with Edgewalker. Certainly a build around card but a powerful one with more than one home.
Jon Irenicus, Shattered One 1
Mostly this is comically bad but it is a Donate effect of sorts which are not the most abundant in the game. I am sure there are things that work well with this, just not well enough for the likes of cube.
Volo, Itinerant Scholar 2
Choose a background is blank text in formats not making use of commanders and the command zone. I think backgrounds are a really good design for EDH. In cube Volo is too slow. You need to untap with him, invest more mana in him, and deploy creatures after him. I suspect this will result in a lot of games where either you or he dies before he draws any cards. What does make Volo interesting is quite how far he can scale. Left in play for too long and Volo will be able to fully refill a hand for two mana! He draws so many cards that you will have to cool off on using it as you will not want to deck yourself! Really this is overkill but at least it is overkill that starts off just being some legs.
White Plume Adventurer 7
This is probably good enough all by itself. It is basically a big Civic Wayfinder. You give the opponent the option to also start going into the Undercity but then you get to go again and likely deeper overall. You being the white player making little dorks implies you will be much better at keeping and retaking the initiative so the symmetry of the initiative seems like a plus in the context of this card. The untap is good too and works with tappers and the likes of Mother of Runes very well indeed. Worst case scenario it is a bit of pseudo vigilance. The only downside to this good little filler card is that you have to then supply the Undercity and ideally the initiative cards with the cube and track them during the game. These things are fun for a while but typically stop feeling like they are worth the extra effort.
Baldur's Gate 3
Now this is a very good reason to play a Gate deck. You need four other Gates in play before this is producing more than one mana making it a bit of a Temple of the False God in terms of ramp but it boosts Gate synergy value a lot, provides coloured mana, and it is useful to some extent before you have a certain threshold of lands. By itself it elevates Gates from a bit of a joke deck to something that might be viable.
Roving Harper 6.5
Shockingly this seems playable. White loves to draw, it loves to have bodies, and it loves things it can flicker to good effect. While no Spirited Companion or Inspiring Overseer it might still just see enough play to hold a cube slot.
Abdel Adrian, Gorion's Ward 1
Too much setup here. Sure, make a load of good EtB dorks, make Abdel, get a bunch of soldiers and then profit. Slowly. Too much setup here and not enough bite for a card this high up the curve.
Lulu, Loyal Hollyphant 1
Fairly easily abused but likely not worth it. Baseline this is too vulnerable for the cost.
Commander Liara Portyr 1
I really like the design here but there are several problems here for a 1v1 card. X being capped to 1 is a shame and Liara being a gold five drop with 3 toughness and little else to make her an impressive body for use in combat kills her chances entirely. At least she doesn't have to attack herself to get the perk.
Ellyn Harbreeze, Busybody 0
Loving the white card draw but a four mana 2/4 with a conditional tap ability is not getting it done.
Aarakocra Sneak 0
Not close to the requisite power level, this could have 4 power and I still wouldn't play it. I don't know what I am expecting though, it is a stock filler common after all.
Nice card to have but flicker effects want to be cheap much more than they want to have value and so I cannot see myself ever running this in a flicker deck.
Goggles of Night 0
Nice effect but multiple layers of conditional on top of an overly high mana investment.