Written by Philippe Saner
Deserts. Gates. Caves. Urza'ses. And now, your own creation.
But how to do it right?
I'm a huge fan of nonbasic land types, both as a player and as a designer. So I've spent a lot of time thinking about this. And looking at the various nonbasic types in custom and in canon, I think the difference between the good ones and the bad ones is pretty straightforward.
A good nonbasic land type has a solid mechanical identity.
Without one, why even have the type? Presumably, it's there to connect the lands both thematically and mechanically. Which means people are going to want to build decks around it. Which, in turn, means that you need to think about how those decks will look. A good mechanical identity provides unique and interesting deckbuilding opportunities; a lack of one provides a frustrating waste of time.
This is not particularly complex or mysterious, but it won't happen by accident. Most of the types I've seen do not hold together well mechanically. A solid mechanical identity has a lot of moving parts, and you need to pay attention to each of them.
The benefits need to fit together
Obviously, nobody's gonna play lands without some advantage over basics. So every nonbasic land, typed or not, needs some kind of perk. The usual ones are "it can provide multiple colours" or "it has a spell-like effect".
These perks should be designed as a group. They're meant to be played together, presumably, and their flavour is meant to be unified. If you want an example of this done well, look at Gates or Urza's lands. You know exactly what you're getting: lots of colours, or lots of colourless mana. You can build with that in mind. If you want an example of this done badly, look at Spheres. Have some oil counters, they say, or hit poisoned opponents harder, or cash in your lands for cards, or save up for expensive land activated abilities...it's a mess. No deck naturally wants all this stuff. Caves aren't great at this either, but Spheres are far worse.
If you have a common cycle, particularly a ten-card fixing cycle, pay special attention to it. People are going to see a lot of it; it will define the land type to them. Make sure the rest of the land type works with it, not against it.
Incidentally, while using similar abilities on all your lands can provide some unity, it does have one significant danger. If they all cost mana, and they can all be used each turn, they're all eating each others' lunches. Watch out for that.
The drawbacks need to fit together
Just as obviously, nonbasics shouldn't be strictly better than basics. Most of them enter tapped (at least sometimes), provide colourless mana, or cost life. And when they do something impressive, they often make you jump through some kind of hoop.
Drawbacks, costs, and hoops should be designed as a group. They don't all need to be the same, but they should all fit together. Take particular care with colourless lands, which do not play nicely in colourful decks. Once again, we can take Urza's lands as a positive example and Spheres as a negative one; Urza's lands are all colourless so you just play a monocoloured deck with few pip-intensive cards, while Spheres are actually trying to get you to play a five-coloured deck with five monocoloured taplands and four mostly-colourless lands. Which is just unworkable.
One again, this is all doubly true of any common cycle.
The payoffs for the land type need to synergize with each other and with the lands themselves
Make sure that the cards rewarding people for using your land type work. With each other, and with the things they're meant to reward.
The negative example here is Caves. They've got a three-mana token-maker that curves into a four-mana board-sweeper. They have graveyard synergies, but their card-selecting creature goes out of its way to avoid stocking your grave. Many of the payoffs work poorly with the discover ability on the common Cave cycle—in the case of Bat Colony, frustratingly so. And so on. These cards just don't want to be in the same deck, no matter how loudly they claim that they do.
Also, if your lands do something cool, best to have the payoffs care about that cool thing. There's nothing wrong with "if you control an X" but there's nothing really right with it either; try and connect to the most appealing aspect of your lands.
Which colours? Which archetype?
When somebody (me) sets about building a deck for your type, they (I) should know what kind of deck they (I) have to work with. Lightning-fast red aggro? Green-based rainbow ramp? Self-milling midrange, with the colours flexible? Pretty much any answer is fine, but there needs to be some answer. You don't want half the cards saying aggro and the other half saying control—there's no way your project is large enough to support both on one land type.
Answering this pair of questions brings together the three previous points. If you're trying to support aggro, you don't want taplands. If you want colourful decks, the lands better provide good fixing. If the archetype is supposed to be slow, don't make payoffs designed to kill the opponent quickly. And so on. The intended deck style should bring the benefits, drawbacks, and payoffs of the land type together.
(Most existing land types tend slow, so there's some unexplored design space in fast land-type-oriented decks. I encourage you to check it out.)
It's probably possible to go too far with this, to be too rigidly prescriptive. But I've never seen that happen. And I've seen the opposite many times.
Should every land in the deck belong to the type in question?
This is an easy issue to miss, but an important one. Some types, like Snow, want to replace your entire manabase. Others, like Urza's, don't. Think about which kind you're making; if you want to see full manabases of your type, make sure you print enough typed cards to make that possible. If you don't, avoid payoffs that scale linearly with the number of the type you control.
It's not much fun when your cards want you to play 24 Caves, but you can't possibly get that many Caves without playing many colours, many colourless lands, and no duals.
Well, that's about it. If you're not sure whether you understand, take a look at the Deserts from HOU and the Deserts from OTJ. If you can see why the HOU Deserts are much better designed, then you get it.