Recently, Wizards of the Coast revealed that the Onslaught fetchlands are being reprinted in the next expansion, Khans of Tarkir. This revelation has naturally elicited a mixture of reactions, but the most amusing have been expressions of confusion by newer players, unfamiliar with fetchlands. Several times, I've seen newer players ask why these lands are better than Evolving Wilds. I've even seen some cases in which apparent veterans of the game dismiss fetchlands as overhyped cards, not actually worth playing. Since this is the CPA, most of my audience has been around for a while, but for those who don't know, an explanation is in order. How are fetchlands good? Let me count the ways...
1. They provide mana-fixing with no tempo loss.
The original fetchlands were actually printed in Mirage (something that, because my audience has been around for a while, you probably already knew). Flood Plain, Grasslands, Bad River, Rocky Tar Pit, and Mountain Valley were just like the later Onslaught fetchlands, except they didn't cost life to activate and the lands they fetched entered the battlefield tapped. People really did call these cards fetchlands, but only very rarely, as most people didn't call them anything at all: they were not very popular cards. This was because using them resulted in tempo loss. Being able to get either a plains or an island in a white/blue deck is valuable, but needing to wait a turn to actually have that land slows the deck down. And yes, this is the same reason that fetchlands are better than the Return to Ravnica block guildgates.
2. On-demand access to different colors of mana for little cost opens up deck design potential.
Tempo loss is a fairly obvious issue, although apparently not obvious enough. But the main advantage of fetchlands has little to do with their impact on gameplay itself and more to do with the options they open up for deck design. If I want my deck to be almost entirely black, but I also want to use certain blue cards, rather than weakening my deck by running several islands, I can include just a couple of them and use Polluted Delta to fetch one if I need it. If I turn out not to need an island, my Polluted Delta can fetch a swamp instead. Being able to bank on the ease of access to a color of mana that I'm not primarily focusing on lets me construct my deck to be more efficient. It's like having a dual land...
3. They can fetch dual lands.
In Legacy, using a fetchland to search for a dual land is a common occurrence. In Modern, the Ravnica dual lands, also known as “shocklands” are used instead, but the idea is the same. I explained to one player who'd asked about this, “I have a blue/black/red deck. If I draw Polluted Delta, I can use it to fetch Underground Sea or I can use it to fetch Volcanic Island, depending on which one I need. If I don't want to run green as a major color in my deck, but there are a couple of green cards that I want to use, I can have a single copy of Tropical Island and just fetch that with my Polluted Delta instead of needing to include enough green mana sources to draw into them. Fetchlands make access to multiple colors quick and easy.”
4. They shuffle libraries.
The library-shuffling aspect of fetchlands may seem incidental, but in some decks, it's a pretty big deal. Brainstorm, Sensei's Divining Top, Sylvan Library, and such are already pretty good cards on their own. Being able to clear unwanted cards from the top of the library by activating a fetchland makes those cards even better.
Players who were around for Zendikar already know this, but fetchlands synergize very, very nicely with the Landfall mechanic. Back when Zendikar block was in Standard, only the new, opposing-color fetchlands were available as far as most tournament players were concerned. Now, the two will coexist in the Modern format.
6. Delve and other graveyard-fueled cards
Originally featured in Future Sight, Delve is the mechanic for the Sultai Brood in Khans of Tarkir. While fetchlands do not, by themselves, greatly empower Delve cards, they do contribute to making those cards more playable. A fetchland or two can make Murderous Cut or Treasure Cruise just a little bit faster. This concept has already been demonstrated to work in the case of Tombstalker, which has been around for a while. But fetchlands were providing fodder for graveyard-eating cards long before Delve existed. Psychatog was a particularly popular early synergy with the Onslaught fetchlands when they were first printed. Grim Lavamancer is another card that benefited from the printing of fetchlands. While those cards have faded in prominence, they've been replaced by other cards that can still use cards in graveyards as fuel, such as Deathrite Shaman.
7. Threshold and other graveyard-dependent cards
While Delve operates by taking cards out of a graveyard as a cost for something, there are other cards, such as those using the Threshold mechanic, which become better due to the mere presence of fetchlands in one's graveyard. But it's not just Werebear and friends that benefit here. Fetchlands provide an easy way to give Tarmogoyf +1/+1. Knight of the Reliquary is well-known as a powerhouse, but part of its reputation comes from how well both of its abilities work alongside fetchlands.
A soon as Crucible of Worlds was released, players began using it with fetchlands. For the cost of some life, it is possible to have a guaranteed land drop every turn (and even to choose which type of land to find), even while not drawing land at all. Before Crucible of Worlds, Cartographer was used in Standard decks with fetchlands. Recursion makes fetchlands especially potent in Life from the Loam decks. What all of these cards have in common is that they enable a single fetchland to be reused, and they do so as a side effect of providing some other advantage.
9. Paying 1 life really isn't that bad of a deal
Some new players have trouble evaluating the cost of fetchlands, along with the benefits. There are different ways of looking at it, but the most straightfoward is probably this: that single point of life paid for a fetchland is only relevant as a cost if it made the difference between winning the game and losing it. Games in which it does come down to that last point of life do happen, but more often than not, it doesn't work that way. For decks that can use any of the advantages of fetchlands (even just mana-fixing), the benefits easily outweigh that minor drawback. One person asked me about the problem of fetchland activations adding up to a sizable chunk of life, but this does not typically happen, as most decks that use fetchlands only have six to eight of them, and when fetchlands are used with recursion, the decks doing so have ways to make the repeated fetchland activations worth it.
The theory behind the use of fetchlands for deck-thinning is that by pulling a land out of one's library, that library now has fewer lands in it, which means that subsequent draws are more likely to be spells, rather than lands. The merits of this have been debated for a long time, with some attempts at statistical analysis on both sides. While I'm sure that such analysis is fun, all that it really does is show that most Magic players who attempt to do statistics do not understand what a confounding variable is. Without going into the details, I'll note that the deck-thinning provided by fetchlands is usually very minor. It can become more or less important depending on the types of decks involved, but it isn't the primary purpose behind using fetchlands anyway. This is why one doesn't typically activate a fetchland right away. Fetchlands are typically saved for when a shuffle effect is needed, when access to mana of a certain color becomes a priority, when it is possible to dodge targeted land destruction, or when it's necessary to get mana from the land that is to be fetched. If deck-thinning were the primary goal, everyone would be activating those fetchlands right away. However, in the long run, fetchlands can provide a very real deck-thinning advantage. This is probably most visible in control vs. control matches, but it can turn up elsewhere too. In some cases, deck-thinning wouldn't be worth the risk by itself, as the life loss could matter more, but deck-thinning is really more of an afterthought. It's a benefit that complements the other advantages of fetchlands.
While a single deck is probably not going to take advantage of all ten of those uses for fetchlands, most decks can benefit from fetchlands. And this sheer versatility makes them a great addition to any Magic player's arsenal.