Think way, way, way back in your cube history. If you're anything like me, you started out playing with something resembling a 360 power-max cube, whether that was powered or unpowered or whatever. We're talking pure good stuff here, no archetypal support at all. The MTGO Legacy Cube is a perfect example. Now, think: what do people get excited about in these sorts of cube environments? What is it that piques the interest most of the people who draft these archetype-less cubes? Let's take a look at some of the cards most beloved by the legions who draft Legacy cube on Magic Online.
What do all these have in common? They're the cards that decks get named after. Everyone's heard of the Opposition deck; everyone's heard of the Wildfire deck; everyone's heard of the Recurring Nightmare deck. The reason these cards get hyped is because they provide archetypes in a world full of good stuff decks. An MTGO drafter can take one of these cards P1P1 and move in, making an interesting deck that plays completely distinctly from decks that don't contain the namesake card. The card defines the archetype: having the card in your deck is necessary and very nearly sufficient to be in that archetype.
The MTGO cube and others like it use this aspect to add some archetypal depth to a format where there was none before--you can cheaply (in terms of cube space) add a lot of depth to your drafting experience when there are single cards that, by themselves, add a whole new play pattern to the set of things your cube can yield. If it works well for them, why not us?
Compact and Single-Card Archetypes in Riptide Design
There's no reason the presence of large macro-archetypes in our cubes should preclude the existence of these tight archetypes, and indeed I think there's been some effort toward identifying the cards that enable such depth, though perhaps not with the idea of compactness in mind. Cards like Seasons Past and Mystical Teachings and their popularity here illustrate that this idea has some appeal.
In addition, it's clear that cube space is at a premium. We all have so many cards we love and want to play with as much as possible, and 360 (or 420 or whatever your cube size is) is a pretty tight space to work in. In fact, people are so interested in increasing the depth and diversity of their cubes that we semi-recently had a whole thread devoted to the idea of opening up spell slots by drastically cutting into land sections. I think introducing a number of single-card and other compact archetypes constitutes a much more measured approach that will help alleviate the same problems, without requiring a bottom-up cube redesign. Let me show you what I mean.
This card's had its fair share of talk here, and people have generally been on board for the card. In fact it's what got me started on this train of thought in the first place! Fond memories of Standard decks sideboarding into Seasons Past to completely alter their plan and go long and deep into games sparked thoughts of how this card really does add a whole new dimension and play pattern to a deck of Magic cards simply by its inclusion. When you make a deck that includes Seasons Past, you've committed yourself to a game plan that is both interesting and entirely unique to Seasons Past. Seasons Past is fun.
Now don't go thinking this is a whole post about Seasons Past: there are lots of places to apply this kind of thinking, but Seasons Past is one of the few cards that's able to fill this role in pretty much any Riptide cube. There's lots of these compact archetypes, but here's the kicker: many of them rely on other cards in your cube to enable them and allow them to realize their potential. I suspect that's a lot of the reason why these cards haven't been so actively and directly sought out on this forum until now.
Context-Dependent Compact Archetypes
Most of the cards that are going to fill this role ask a little bit of you and your cube before they just go to work making your drafts and games deeper and more diverse, and this exists on a spectrum. On one end you have your Mystical Teachings, which merely demands that you give it a healthy complement of instants and Flash spells before rewarding you with a delicious new toolbox archetype. On the other end of the scale you have Laboratory Maniac, which lures you with the promise of winning the game in an exciting way but asks you to build your cube in a manner that allows your drafters to fully empty their libraries.
All of these cards ask different things from you, but there are many cards in this vein and they all have different requirements. You can find cards whose requirements line up with what's already in your cube and will reward you with depth basically for free, without you having to appreciably change your cube's composition at all. Let's look at my Cube Eternal as an example. It's not a perfect cube, particularly since I recently made some large changes, but it illustrates the concept well.
Genesis is a creature that can really pay you off, but it asks a couple things from you: you must be able to put Genesis in your graveyard, and you must have creatures worth recurring. In a cube where recursion of small creatures is a priority, and where discarding cards is both readily available and useful in a number of ways, Genesis doesn't ask anything from the cube that it's not already doing. So the only cost to the cube is exactly one slot, and it's not as if Genesis is even competing with other green five-drops--your plan shouldn't be to cast it anyway.
Speaking of not casting it anyway. Cards that you never intend to cast make an interesting sort of engine, one that can go in all sorts of decks. They split their playability in decks not along the color pie, but along the archetype spectrum, which is a really interesting design aesthetic and makes for refreshing gameplay while cutting (some) parasitism.
The category of context-dependent single card archetypes feels really large--you can really pack your cubes with this kind of card if you want, and every (synergy based) cube is going to have a lot of mechanics that will naturally play into some build-around or another. It's just a question of identifying what kinds of environments your cube will create more often than most, then finding cards that thrive in the environment while being unique one-card archetypes. The real advantage here is you get build-arounds in your draft, without having to build your cube around them.
Hybridization and Single-Card Archetypes
An additional benefit of single-card archetypes is their propensity for hybridization when built into a cube this way. It's not at all uncommon that a deck would have more than one of these single-card plans in the same deck, which just means that there are even more combinations. The more you can build in additional angles that can graft onto your existing archetypes, the more variable and deep your drafting experience.
This lovely idea, which I dredged up from here (thanks vennythekid) takes two cards that independently add a lot of depth and uniqueness of play to a deck, and combines them in an interesting way. In fact, it's my opinion that any combination of the following makes a fun synergistic deck: Doomsday, Laboratory Maniac, Seasons Past, Elixir of Immortality. With the addition of these four cards, there's six interesting combinations and deck identities that have been added to the cube. Hybridization is what really allows you to get a lot of bang for your buck in getting new deck plans, which is really what it's all about: roughly taking the Making Control Decks Interesting thread and applying it to everything in your cube, control or otherwise.
What do all these have in common? They're the cards that decks get named after. Everyone's heard of the Opposition deck; everyone's heard of the Wildfire deck; everyone's heard of the Recurring Nightmare deck. The reason these cards get hyped is because they provide archetypes in a world full of good stuff decks. An MTGO drafter can take one of these cards P1P1 and move in, making an interesting deck that plays completely distinctly from decks that don't contain the namesake card. The card defines the archetype: having the card in your deck is necessary and very nearly sufficient to be in that archetype.
The MTGO cube and others like it use this aspect to add some archetypal depth to a format where there was none before--you can cheaply (in terms of cube space) add a lot of depth to your drafting experience when there are single cards that, by themselves, add a whole new play pattern to the set of things your cube can yield. If it works well for them, why not us?
Compact and Single-Card Archetypes in Riptide Design
There's no reason the presence of large macro-archetypes in our cubes should preclude the existence of these tight archetypes, and indeed I think there's been some effort toward identifying the cards that enable such depth, though perhaps not with the idea of compactness in mind. Cards like Seasons Past and Mystical Teachings and their popularity here illustrate that this idea has some appeal.
In addition, it's clear that cube space is at a premium. We all have so many cards we love and want to play with as much as possible, and 360 (or 420 or whatever your cube size is) is a pretty tight space to work in. In fact, people are so interested in increasing the depth and diversity of their cubes that we semi-recently had a whole thread devoted to the idea of opening up spell slots by drastically cutting into land sections. I think introducing a number of single-card and other compact archetypes constitutes a much more measured approach that will help alleviate the same problems, without requiring a bottom-up cube redesign. Let me show you what I mean.
This card's had its fair share of talk here, and people have generally been on board for the card. In fact it's what got me started on this train of thought in the first place! Fond memories of Standard decks sideboarding into Seasons Past to completely alter their plan and go long and deep into games sparked thoughts of how this card really does add a whole new dimension and play pattern to a deck of Magic cards simply by its inclusion. When you make a deck that includes Seasons Past, you've committed yourself to a game plan that is both interesting and entirely unique to Seasons Past. Seasons Past is fun.
Now don't go thinking this is a whole post about Seasons Past: there are lots of places to apply this kind of thinking, but Seasons Past is one of the few cards that's able to fill this role in pretty much any Riptide cube. There's lots of these compact archetypes, but here's the kicker: many of them rely on other cards in your cube to enable them and allow them to realize their potential. I suspect that's a lot of the reason why these cards haven't been so actively and directly sought out on this forum until now.
Context-Dependent Compact Archetypes
Most of the cards that are going to fill this role ask a little bit of you and your cube before they just go to work making your drafts and games deeper and more diverse, and this exists on a spectrum. On one end you have your Mystical Teachings, which merely demands that you give it a healthy complement of instants and Flash spells before rewarding you with a delicious new toolbox archetype. On the other end of the scale you have Laboratory Maniac, which lures you with the promise of winning the game in an exciting way but asks you to build your cube in a manner that allows your drafters to fully empty their libraries.
All of these cards ask different things from you, but there are many cards in this vein and they all have different requirements. You can find cards whose requirements line up with what's already in your cube and will reward you with depth basically for free, without you having to appreciably change your cube's composition at all. Let's look at my Cube Eternal as an example. It's not a perfect cube, particularly since I recently made some large changes, but it illustrates the concept well.
Genesis is a creature that can really pay you off, but it asks a couple things from you: you must be able to put Genesis in your graveyard, and you must have creatures worth recurring. In a cube where recursion of small creatures is a priority, and where discarding cards is both readily available and useful in a number of ways, Genesis doesn't ask anything from the cube that it's not already doing. So the only cost to the cube is exactly one slot, and it's not as if Genesis is even competing with other green five-drops--your plan shouldn't be to cast it anyway.
Speaking of not casting it anyway. Cards that you never intend to cast make an interesting sort of engine, one that can go in all sorts of decks. They split their playability in decks not along the color pie, but along the archetype spectrum, which is a really interesting design aesthetic and makes for refreshing gameplay while cutting (some) parasitism.
The category of context-dependent single card archetypes feels really large--you can really pack your cubes with this kind of card if you want, and every (synergy based) cube is going to have a lot of mechanics that will naturally play into some build-around or another. It's just a question of identifying what kinds of environments your cube will create more often than most, then finding cards that thrive in the environment while being unique one-card archetypes. The real advantage here is you get build-arounds in your draft, without having to build your cube around them.
Hybridization and Single-Card Archetypes
An additional benefit of single-card archetypes is their propensity for hybridization when built into a cube this way. It's not at all uncommon that a deck would have more than one of these single-card plans in the same deck, which just means that there are even more combinations. The more you can build in additional angles that can graft onto your existing archetypes, the more variable and deep your drafting experience.
This lovely idea, which I dredged up from here (thanks vennythekid) takes two cards that independently add a lot of depth and uniqueness of play to a deck, and combines them in an interesting way. In fact, it's my opinion that any combination of the following makes a fun synergistic deck: Doomsday, Laboratory Maniac, Seasons Past, Elixir of Immortality. With the addition of these four cards, there's six interesting combinations and deck identities that have been added to the cube. Hybridization is what really allows you to get a lot of bang for your buck in getting new deck plans, which is really what it's all about: roughly taking the Making Control Decks Interesting thread and applying it to everything in your cube, control or otherwise.