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
Soul Partition 4
I love the design of this one but I fear it is one mana off being amazing. If this cost one or if the cost increase was three mana to play from exile and not two then there is a good chance this would be one of the best removal spells in the game. As it stands I think I prefer the card parity offered by the likes of Unexpectedly Absent over the tempo this offers. Much as I rave about tempo this is a removal spell that doesn't remove anything. It is thus effectively a bounce spell, and a good one at that but you just don't need to resort to that extreme in white where strong and cheap removal is abundant. Fateful Absence kills the problem at the same cost rather than delay it etc.
Transmogrants Crown 6.5
Strong card in a black deck and I think still fine in others. Bonesplitter is a fine card. It turns any dork into a relevant one and the card cash in is lovely. Black likely needs this least with Green and White most impressed. This certainly is no bomb. White already has Halvar, and his more impressive back end! Halvar (Sword of the Realms really though) is good but it is no bomb and all this really has over Halvar is playability in other colours. I'll give this a little test but I fear it will just not make many lists being a bit aimless, it is slow unreliable card advantage and a relatively low tempo aggressive tool. Power wise this is just about there but I think it sits in a bit of a dead zone between value and tempo where it is just that bit too slow for the aggressive decks and a little too demanding of support in slower decks. Midrange decks want all their cards to be stand alone good where possible and those that are not need to be essential like removal or complete bombs - which this is not. There are just so many other cards competing for space in decks that need dorks to do anything. In that much smaller and much more fiercely contested group this no longer stands up so well. Shame, it is a nice, and arguably fixed Skullclamp looking card. Certainly getting some testing in with it, if just because I quite want to paly with this card!
Hurkyl's Final Meditation 3
10 is a bit much for Time Stop or Cyclonic Rift. Getting both is tempting but 10 is a foolishly large amount of mana that you really need to cheat on. Torrential Gearhulk likes the look of this one very much indeed. Not enough to make this good in cube I would wager. If this were a seven mana instant speed bounce everything card with a kicker for 3 that ended the turn then it would be a really good and scary card which is interesting from a card design point of view but I realize very meaningless in the real world!
Drafna, Founder of Lat-Nam 2
Lots of card here but not only do you need artifacts to go with this you also need to dump mana into it making it all a bit narrow and unlikely to do much. Mox Training Ground for infinite storm? That kind of combo is ten a penny these days. You need abusively good EtB effects on artifacts to make Drafna a card, and probably a lot of mana production too.
Overwhelming Remorse 6
Sadly this scales the wrong way in that it is cheap late when you have most mana while costing the most early. I like this more than Murderous Cut at least, it isn't directly better but does sit more comfortably in cube. Hard to ignore a one mana instant speed exile removal spell that hits walkers and dorks. Especially one you can still use without any support and that doesn't consume any other resources like life or stuff in the bin. This is a card that is competing with the likes of Hero's Downfall and not actual one mana removal. I do quite like the idea of this as it can be very powerful and swingy in the mid and late game where more typical cover all removal remains pretty cumbersome and hard to leverage. Certainly one to be tested but I fear too few decks are keeping three or four dorks in the bin consistently enough to keep this performing well. Ultimately I think you will lose more games where this costs more than three and you can't kill something you need to than you will win be virtue of this costing less than three allowing you to make that big turn happen.
Stern Lesson 4
Well, I guess we need to talk about powerstones then. If you build around them they are going to be great. Likely better than Llanowar Elves. If not then they will be pretty limp. I did a quick estimation of what a powerstone would help with in my cube and about 20% of the things would get assistance with the payment of an ability and 4% of things could be helped cast with a powerstone. Notably the best things of the 20% were also part of the 4%. Signets, Walking Ballista, Reckoner Bankbuster etc. Also notably there was not that much I was excited to support the paying of activation costs for in the colours. Generally they were quite low impact or late game abilities. Very few in blue as well. Ultimately powerstones outside of an artifact heavy, themed or synergy deck seem to be fairly low value while in them however they are a good 50% of a Sol Ring. Generally give me a treasure over a powerstone in cube draft basically. Probably give me blood or a clue as well. The costing on powerstone generation also seems a little bit too much for cube. They should be cards in supporting roles but cost too much to be usable as a support card. I don't even know if I would play a 1 mana Powerstone in cube. I probably would want to but in order to make it worth doing I imagine I would need to support it a little better, which would at least be easy to do.
Anyway, is this good? Well, it isn't bad but as discussed, powerstones are not doing enough and this costs too much for the sort of card it is anyway. So no, it isn't good for cubes, but you could easily make it so if you wanted to and it is absolutely the kind of card that it is a lot of fun and well worth making playable.
Yotian Dissident 1
This is too narrow to be anything other than a pure build around. It is very powerful but sadly you cannot really afford these kinds of payoff in the artifact synergy deck. This isn't an artifact and it has too many coloured mana symbols. It can do great things but it just isn't getting a look in. Yes, it is super cool with modular but then so is Throne of Geth and you can cast that....
Argothian Opportunist 1
The green take on Stern Lesson. Seems like convenient powerstone generation is going to be kept to three mana minimum. This is seemingly decent but too narrow, linear, and fair for cube. Green is always going to be the least interested and impressed with powerstones on top of that given that it has actual ramp all to itself.
Bitter Reunion 4
Nice take on Tormenting Voice. I am more interested in the ability to have this in play for devotion or flickering or sacrificing to something else than I am for giving my stuff haste but it is all quite interesting. This seems more powerful than most of the other red cards like this however I suspect they will typically wind up getting more play as they pair up better with the likes of Forks and Past in Flames.
Skitterbeam Battalion 6.5
This hits pretty hard and pretty reliably but it is just a beater. Without something like Purphorus or Goblin Bombardment or some other card that is scaling nicely with many dorks in one card this isn't exciting enough. Yes, this hits harder than the various top end red hitters but it lacks any of the utility, disruption, and value that comes with Glorybringer or Emissary of Grudges. If you have a very large number of things that scale with Skitterbeam then it is probably good in your cube, although perhaps not better than Siege-Gang Commander, if not then probably play a more rounded card. This is a strong card but it sits on the edge as far as cube goes and thus needs those external reasons to tip it over the edge and make it properly enticing.
Tocasia's Welcome 6.5
Lovely to see a white value card. This might well be better than Welcoming Vampire. It isn't easily removed, it isn't kiboshed by having Anthems in play boosting your dorks out of range, it has a much higher hit rate in general as well. This is however a low tempo card you play in an aggressive deck than wants tempo. It is not a threat either and so it is fighting for space against creature buffs and removal. I fear that despite this being better at what it does than Welcoming Vampire you will often play Vampire simply to keep that dork and threat count high. Good card of sufficient power but I would bet on it not lasting in many cubes.