Prismatic Ending 7
A sorcery speed Isolate with some rather potent scaling. Sadly it scales up with colours of mana rather than just mana making it rather the gold card. If you have access to all five colours this is premium removal. Access to three makes this good removal. Access to just two colours makes this on the mediocre side and in a mono coloured list it is just not doing enough. I cannot easily evaluate this as I normally do. It is effectively a gold card but while I would say it needs three colours it certainly isn't narrow in the way a three colour gold card is. You don't even "need" those extra colours. You can play this in a two colour deck and toss in a few spare duals or what have you. When a card is fine with base colours and just gets better with more it is a far easier and more convenient splash. Kenrith, Valki, or Plaarg are examples of this. They are soft gold rather than hard gold if you will. Prismatic Ending is the perfect one for one removal as it goes 1 for 1 on both cards and mana. While 1 for 1 removal that cannot get tempo isn't that exciting sounding, especially for a gold card there are some very strong perks with this. Broad target range and exile certainly are great. The extra perk this has over so much that is so broad in range is that you can use this early in the game to handle a cheap card. You cannot take down a Soul Scar Mage with a Vindicate in good time. You can with Ending. I think that is enough to tip it over the edge and make it cube worthy. I suspect I will see this in decks that are splashing white rather than being heavy white. It smacks of a green card as far as cube is concerned!
Squirrel Sanctuary 4
I love this card. Cheap, useful, ongoing, cute, flexible, option rich, synergic. I want it to be good more than it is sadly. It is an amazing support card for the right deck but that is not a limited cube deck. You want more punch in those and punch this lacks. A one mana 1/1 followed by two mana 1/1s if you have a mana spare when your non-token dorks die. Hardly gripping stuff. You really need those tokens to do a lot of work before you can call this value. Two permanents in one very cheap card is always good to see. I expect to see this in decks beyond just tribal, enchantress, and aristocrat lists and already having three potential homes is impressive. Cheap support cards are in high demand!
Ravenous Squirrel 7.5
This is a beast of a card. It threatens to get very large very quickly in certain kinds of deck. Despite being a synergy card I expect this is still good enough to perform in cubes. A little like Champion of the Parish. While this will be far more potent in decks built around doing things that trigger it there is plenty in cube that passively does for this little 1/1 to get good work done. We have clues, treasure and food. Tribe Elders, Village Rites, Baubles, Chromatic Stars, Carrion Feeders, Priest of the Forgotten Gods, Retrofitter Foundry, Yawgmoth. The list goes on and on. The activated ability is great too. It helps it grow when there is nothing passively doing it and allows you to cash things in for life and cards. It isn't super mana efficient but it is a pretty reasonable rate. You don't need it for the card to be good but it does push the card quite a lot, especially in cube. Sac outlets are nice and ones with a lot of scope and good returns are always welcome. This card is very playable and offers synergy and utility while also being a pretty scary threat. It will massively empower some decks and fit neatly into many more.
Squirrel Sovereign 2.5
A strong lord for a tribe that is getting a lot of love at the moment. A tribe that also really suits a lord as it goes wide pretty well. This gets upgraded in rating as the tribe improves. I am presently assuming squirrels are viable but not top tier. It will not take much more of the quality we have seen here for them to jump up the tiers though.
Chatterfang, Squirrel General 5
Potent in both mass token decks and squirrel decks. The body is also fairly reasonable baseline so while you do need support for Chatterfang to perform you don't need all that much. Cool card, plenty of potential homes and no slouch on power. Not quite enough general support in draft cubes for this to be worth it given that you do somewhat want this to have access to black mana. Close though which is scary for a card that is so clearly a tribal synergy card!
Fractured Sanity 6
This is a filthy powerful mill card. It hits very hard, is cheap, it is mono coloured, and it has two modes of action depending on your card/mana situational needs. This is one of the best mill card for cube. Mill is super tedious in 40 card decks and not all that fun to play against regardless of deck size. I recommend against supporting it in your cubes. If you are sadistic enough to support mill in your cube then this is top rate. Just know that you are a bad person.
Serra's Emissary 1
This is pretty underwhelming. It hits that trough between top end playables and things you recur, being too costly for the former and too weak for the latter. This does lock out some decks but not enough and not in an interesting or powerful way. Chose creatures and win if they don't have removal. Fun. It isn't even all that good when naming non-creatures. Removal options are found on so many types you are unlikely to protect against much. Even narrow lists like storm will have ways to play around this without having to answer it. Iona this is not. Feels more like a Pristine Angel, Blinding Angel, or even just a Beloved Chaplain!
Break Ties 3
At first glance this seems too expensive for what it offers. The effects either struggle to be worth a card or struggle to be worth the mana. At two to cast I would be more keen. I will give this a little test as white hungers for utility but I have very low hopes. You don't really want it at all if you can't use the reinforce to good effects which makes most of the slower decks decidedly disinterested.
Late to Dinner 2
Nice to have some Resurrect redundancy but this isn't really what white is about nor is this card very exciting power wise. A food is not making much difference to a four mana card's power level (obviously unless it uses food somehow like Wicked Wolf...)
Spreading Insurrection 1
Too narrow to rely on as a win condition. Perhaps a Wish target you might have for a storm or storm like deck. This can fairly easily win the game in the right setting with a low storm count, the kind you could muster with Lava Dart, Gut Shot and the like but it is still just way too situational to be running.
Lucid Dreams 0
Cute scaling that just screams Emrakul the Promised End. Sadly the card is a five mana sorcery that has a shocking floor and not all that exciting of a ceiling all things considered.
Tourach's Canticle 0
Super Stupor tra la la la la laa laa. Far too slow for cube.
Rise and Shine 2
Useful redundancy and some nice flexibility on use. Needs a build around and isn't all that powerful itself, not at two mana at least.
Sword of Hearth and Home 6
I like the effects on this Sword's triggers and the protection is fairly useful as far as connecting goes. This isn't better than Fire and Ice although it might be the second most suitable for cube play, even if it is not the second most powerful. It isn't as oppressive as some Swords nor as narrow as others. It does interesting and generally useful stuff too. I like it and will give it a little test but mostly I think this just lacks the raw power to last in my cube. My cube has only had room for one Sword for absolutely ages now. I occasionally try out a second for a bit and it just fails to get any play or do much of anything. I do think this would be my first choice for second Sword if somehow my cube does want that second one but that isn't much of an accolade.
Void Mirror 1
Very potent card that will do a lot of work in older formats. This is a Chalice of the Void or Trinisphere sort of card but mostly just for the eternal settings, I am not even sure this does all that much in modern. It certainly isn't all that exciting for cube. You would need to have an incredibly heavily artifact synergy cube for it to be good and then it is probably just oppressive and lacking in fun. Still, a big card as far as impact on the game. A sideboard card for constructed events in cube style play at best really.