GENERAL NOTES
This Cube was formed by taking a look at what I wanted each of the ten color-pairs to be doing, and then making a somewhat-realistic Limited deck based on those archetypes. I then jammed all ten of them together. The Cube features some "commons" (the four-ofs), some "uncommons" (the two-ofs), and some "rares" (the one-ofs). This let me better control what I wanted each color to do, rather than being limited to a singleton environment, which would limit my options (the rarities chosen for each card mostly, although not completely, match their rarity in their native real Magic sets). I also went ahead and included 8 of each guildgate, so that if you want to branch out into other colors, you can more easily do so, as well as pick up any color-fixing if you need to. Below I will briefly explain each color-pair's deck archetype, and provide 10 example cards of what to look out for when drafting it in this Cube.
AZORIUS
Most sets have "flying creatures" as the Azorius draft archetype, and this cube is no different. The primary card that makes this deck work is Thunderclap Wyvern. It also uses a lot of tokens, from Thopters to Spirits. You can swarm the board with efficient flyers quite easily. (Notable cards: Aviation Pioneer, Cyclone Sire, Djinn of Wishes, Exclusion Mage, Healer's Hawk, Luminous Bonds, Oddly Uneven, Talon Trooper, Thunderclap Wyvern, Triplicate Spirits)
ORZHOV
The Orzhov deck is all about creating a bunch of tokens. Triplicate Spirits, Call to the Feast, and Spectral Procession are all good pickups for this deck. Once you've created a lot of tokens, you can use either Earth-Origin Yak or Kongming, "Sleeping Dragon" as your payoff for doing so. There's also some cards like Bloodthrone Vampire that can help you here, but be warned: sacrificing them may not be to your advantage, since it means you won't have them around later for other potential payoffs. Bloodthrone Vampire is a bit of a risky play in the Orzhov deck here, it's more suited for Rakdos. But if you want to branch into tri-color and go Mardu, then go for it. (Notable cards: Call to the Feast, Dawn of Hope, Doomed Dissenter, Doomed Traveler, Earth-Origin Yak, Endless Obedience, Fungal Infection, Spectral Procession, Triplicate Spirits, Utter End)
DIMIR
Every set seems to have one color-pair that wants to be a control deck. For this cube, that would be Dimir. The Dimir deck has very efficient removal and counterspells to stall out the game, and then big creatures at the top end of the curve to win. There's also a small theme of cycling+delve. If you get a lot of cards with cycling, you can use them to fill up your graveyard, and then use delve to exile them and cast a big spell relatively early. (Notable cards: Artful Takedown, Crux of Fate, Dead Drop, Devious Cover-Up, Insidious Will, Lay Claim, Murder, Shadowmage Infiltrator, Sultai Scavenger, Treasure Cruise)
IZZET
For most sets, the Izzet deck cares about instants and sorceries, but once in a while, there will be a set where the Izzet deck cares about artifacts. This cube does the latter, and makes Izzet want as many artifacts as possible. You can create a lot of Thopter tokens and also some Treasure tokens too. And there's a lot of ways to get value off of them. Perhaps the most notable is Maverick Thopterist. Get out a ton of cheap artifacts early to cast him ahead-of-curve, and then create two Thopters with him to use later for even more value. (Notable cards: Hammer of Purphoros, Makeshift Munitions, Maverick Thopterist, Prophetic Prism, Rusted Relic, Sage of Lat-Nam, Sailor of Means, Scrapyard Mongrel, Thopter Engineer, Thopter Spy Network)
RAKDOS
The Rakdos deck is all about sacrificing your creatures, which is typical for Rakdos. I guess that does pose a problem, though. You'll run out of creatures, right? Well, that's where your opponent comes into play. If you have no creatures of your own, take theirs instead! There are multiple cards you can get that let you gain control of your opponent's creatures, thus fueling your sacrifice engines. (Notable cards: Bloodthrone Vampire, Brawl-Bash Ogre, Captivating Crew, Fling, Hammer Helper, Keldon Overseer, Makeshift Munitions, Phyrexian Plaguelord, Severed Strands, Thallid Soothsayer)
GOLGARI
When I decided to make this cube, I knew I wanted some silver-bordered stuff in here. But it was hard to find silver-bordered cards that would play well with players who would rather stick to black-bordered cards. Most silver-bordered cards make you do weird and whacky stuff that is not suited for serious play. But there is one exception: dice rolling. Rolling dice is essentially just "choose one at random", which has already appeared in black border several times. So I went with that. Most dice-rolling cards from Unstable are black and green, so it became the Golgari archetype. That's the Golgari deck of this cube for you: just roll a lot of dice. And hey, dice-rolling can be fun! (Notable cards: Chittering Doom, Fertile Ground, Ground Pounder, Hydradoodle, Krark's Other Thumb, Mad Science Fair Project, Murder, Reaper of the Wilds, Squirrel-Powered Scheme, Willing Test Subject)
GRUUL
Most sets don't have a theme that cares about enchantments, but when they do, it is almost always in Selesnya or Orzhov. To help stand out, it's in Gruul here. The Gruul deck cares about enchantments. It also has a fair bit of ramp in it, so that you can get to your powerful enchantments quickly. Because it's hard to see a Gruul deck as an enchantment deck, I'll show off more than ten notable cards so that you can get an idea for what I'm talking about. (Notable cards: Arachnus Web, Cartouche of Strength, Cartouche of Zeal, Enchantress's Presence, Fertile Ground, Forgeborn Oreads, Meteor Storm, Mogis's Warhound, Nyxborn Rollicker, Trial of Strength, Trial of Zeal, Vow of Wildness, Yavimaya Enchantress, Zhur-Taa Druid)
BOROS
Boros decks typically go one of two ways: either you swarm the field with a lot of little dudes, or you get one single dude and voltron it up with a lot of equipment and auras. In this cube, you'll be doing the latter. This nicely crosses over with the Izzet artifact and Gruul enchantment decks, so that way, you can go for tri-color if you want to, and make a Jeskai or Naya deck. Oh, and by the way, there's a fair number of Boros cards here with double strike, which should help your deck be lightning-fast! (Notable cards: Boros Swiftblade, Cartouche of Zeal, Champion of the Flame, Empyrial Plate, Fencing Ace, Healer's Hawk, Heavenly Blademaster, Heirloom Blade, Knight's Pledge, Skyknight Legionnaire)
SELESNYA
The Selesnya deck is full of "enters the battlefield" effects. That sounds a bit odd, but when you remember that white is the color that lets you exile a creature and then return it to the battlefield under its owner's control, you start to see the pieces. You can use this to re-use the "enters the battlefield" effects of your cards. Acidic Slime is a great card as-is, since it can blow up an artifact, enchantment, or land when it comes into play. But being able to do this multiple times? That's even more devastating for your opponent. It can mess up their plans greatly. In fact, it's so good that I'm adding it to my notable cards for the deck, meaning this one will have 11 instead of 10. (Notable cards: Acidic Slime, Armada Wurm, Cloudshift, Crested Herdcaller, Flickerwisp, Intrusive Packbeast, Kor Skyfisher, Pelakka Wurm, Restoration Angel, Saddleback Lagac, Skittering Surveyor)
SIMIC
The Simic deck lets you keep your options open. You can pick up ramp, or +1/+1 counter synergies, or whatever you really need. It's designed to make it easier for you to go into other colors. Why is this necessary? Well, remember how I put 8 of each guildgate in the Cube? That opened the way for a "Gates matter" deck, and so it ended up going into Simic. I think that's the best thing to do if you end up in Simic: take guildgates highly, and then try to get the gates matter cards and branch out into four or five colors. But if that's not your style, there's also plenty of +1/+1 counters and ramp strategies here too. (Notable cards: Circuitous Route, Cloudfin Raptor, Curse of Predation, Fertile Ground, Gatecreeper Vine, Guild Summit, Herald of Secret Streams, Saddleback Lagac, Tatyova, Benthic Druid, Vigean Graftmage)
A NOTE ABOUT SILVER-BORDERED CARDS
Yes, there are a few silver-bordered cards in here. The vast majority of them are to make the Golgari deck function. As I said above, dice-rolling is essentially just "choose one option at random", which is a thing in black-bordered Magic. But I did want all of the silver-bordered cards in this cube to be enjoyable by black-border players, so let's take a look at them in more detail. There's only 21 of them, so this should be quick. Chittering Doom, Ground Pounder, Hammer Helper, Hydradoodle, Inhumaniac, Krark's Other Thumb, Mad Science Fair Project, Painiac, Squirrel-Powered Scheme, Sword of Dungeons & Dragons, The Big Idea, Time Out, and Willing Test Subject are all only silver-bordered because of dice rolling. And if we accept dice-rolling as a thing that black-border could theoretically do, then we're good on that front (and technically, black-border DOES do dice-rolling, namely in Planechase with the planar die, which is even mentioned on the Legacy-legal card Fractured Powerstone!). That's 13 cards out of the way. What about the other 8? Well, let's take a look. Infinity Elemental and Novellamental are both cards with no silver-bordered abilities. Novellamental has even been printed in black-border as Welkin Tern (as long as you ignore the creature type). And Infinity Elemental is just a vanilla. So that's fine. Just Desserts is basically just a 3 damage burn spell. Yeah, it technically does more than 3 damage, but the extra ~0.14 doesn't really matter. More or Less alters the text of a card by replacing one number with another. That sounds not black-border friendly at all, but text-altering does happen in black border from time to time, such as with Spectral Shift. Super-Duper Death Ray is a burn spell with trample, which doesn't work within the rules, since trample is supposed to only apply to combat damage, but if you really think about it, a burn spell with trample is just a cleaner templating for Liquid Fire (which has awfully messy Oracle text). Buzzing Whack-a-Doodle involves secret choices, but that has already been done in black-border with Menacing Ogre and Stalking Leonin. That leaves just two cards. Oddly Uneven is a bit hard to justify. It's half a boardwipe, but based on an arbitrary distinction, and it isn't even fully compatible across all languages. Were this card to be done in black-border, it'd be a nightmare, since you'd have to deal with foreign cards. But there is a bit of a justification that can be done here. Look at the cards City in a Bottle, Golgothian Sylex, and Apocalypse Chime. These destroy all cards from a single expansion. How does the game know what expansion a card was originally printed in? Well, the Comprehensive Rules have a list of each card from each of these three expansions. If Oddly Uneven were to be done in black-bordered Magic, a similar thing would likely be done for it, and the Comprehensive Rules would simply list every card that has an odd-worded or even-worded name. The final silver-bordered card in the cube is Hangman. At first glance, this one is not at all black-border friendly, but at the end of the day, it's just another "secret choice" effect like Buzzing Whack-a-Doodle. I will grant that there is a little more to Hangman than that, particularly because the number of choices you can make is not a small number, but it's still just the same basic effect in principle. So there you have it. All silver-bordered cards in this cube are technically black-border friendly.