What’s the Mana Base Impact of Prismatic Vista and the Mathematical Value of Deck Thinning?

Regular readers may have guessed that I would be the author from the title alone, and they would be right. I like tinkering with mana bases and running the numbers, so I was delighted to see a card in Modern Horizons that allows me to do both.

Prismatic Vista - Foil

Prismatic Vista is basically an Evolving Wilds that puts the land into play untapped at the cost of 1 life. That’s usually well worth the cost.

But Evolving Wilds never saw a lot of play in Modern. Will things be different for Prismatic Vista?

Impact of Prismatic Vista on Mana Bases

At worst, Prismatic Vista is a budget replacement for “actual” fetchlands. In U/W Control, for example, Prismatic Vista is not as good as Flooded Strand because it can’t get Hallowed Fountain, but it still gets Plains or Island, so it’s not much worse. And Prismatic Vista will probably be a bit cheaper.

Besides budget reasons, there are several decks where Prismatic Vista might be better than “actual” fetchlands. For example:

  • 2-color decks that want more than four fetchlands: Many U/W Control decks run one Polluted Delta as a fifth fetch. Polluted Delta can grab Island and Hallowed Fountain, but not Plains. Prismatic Vista can grab Island and Plains, but not Hallowed Fountain. So it’s a trade-off where one is not strictly better than the other. If you want to preserve your life total and don’t have stringent mana requirements (i.e., you don’t want to cast both Path to Exile and Prismatic Vista on curve), then Prismatic Vista could be better as your fifth fetchland. Similar comments hold for Flooded Strand in Izzet Phoenix, Marsh Flats in The Rock, or Windswept Heath in Titanshift.
  • 3-color decks that want to preserve their life total: In a deck like Esper Control, Flooded Strand can get black mana via Watery Grave or Godless Shrine. But again, this often comes at the cost of 2 extra points of life. If you want to preserve your life total and don’t have stringent mana requirements, then using Prismatic Vista to fetch basics may theoretically be preferable over on-color fetchlands. I believe this is a fringe use—actual fetchlands will be preferable for most decks—but not impossible.
  • Snow decks: If you want to exploit Ice-Fang Coatl, On Thin Ice, Skred, and/or Dead of Winter, then you need a lot of Snow-Covered basic lands. In such a mana base, Prismatic Vista is the perfect fixer because it can get the Snow basic of any of your colors.
  • Eldrazi decks: Unlike the old fetchlands, Prismatic Vista can get Wastes. In Red Eldrazi, for example, Prismatic Vista can fetch both Mountain and Wastes, which is something that Wooded Foothills could never accomplish. This represents a big upgrade if you’re looking to cast Eldrazi Obligator.
  • Blood Moon decks: Blood Moon decks generally prefer basic lands over dual lands, so getting additional ways to find the right basic is useful. I imagine that Mardu Pyromancer (a 3-color deck with Blood Moon) will be interested in Prismatic Vista, for example. Or, taking inspiration from some of the categories above, how about Temur Eldrazi Snow Moon? That’s a deck building challenge if I ever saw one.
  • Decks that used to play Evolving Wilds: Evolving Wilds has seen play before at a Pro Tour. This was in a Restore Balance build with Firewild Borderpost, Fieldmist Borderpost, etc. These cards require basic lands, so if you’re interested in revisiting this build, then Prismatic Vista would be a huge upgrade over Evolving Wilds.
  • Commander decks. The vast majority of Commander players will want a copy of Prismatic Vista. This will drive up the price of the card.

The Mathematical Value of Deck Thinning

Fetching a land from your deck slightly decreases your chance of drawing another land in subsequent draw steps, thereby lowering the probability of flooding out. But it also comes at the cost of a point of life. Is it worth playing or using a fetchland for the sole purpose of thinning your deck?

As always in Magic, the answer to this question is “it depends.” But let’s do a thought experiment to gain some intuition. Consider a 60-card mono-color deck with 24 lands. So we’re fetching only to thin our deck, not to fix our mana. We keep an opening hand with three lands and four spells on the play. Since our curve is relatively low, any additional land we would draw in this game is dead—we are only interested in drawing spells from now on. This is a strong assumption. Most decks will have some use for excess lands. But in this thought experiment, we set the value of any land beyond the third to zero.

From this basic setup, I conjure two scenarios. In scenario A, all lands in our opening hand and our deck are basic lands. In scenario B, we replace one of the lands in our opening hand with a Prismatic Vista, and we crack it right away on turn 1.

In any case, we then draw N cards from the top of our library. In scenario A, that means drawing from a 53-card library with 21 lands. In scenario B, we’re drawing from a 52-card library with 20 lands. In either scenario, we can straightforwardly determine the expected number of spells drawn in N draws. We then consider the difference between these two numbers. This represents the expected number of extra spells drawn as a result of thinning our deck.

A graph that shows the number of draw stages versus expected number of extra spells.

So after five draw steps (or more generally, drawing five cards, possibly via cantrips) we have drawn 0.058 extra spells in scenario B compared to scenario A. That’s approximately 1/17th of an extra spell. Is that worth 1 point of life? Well, if we’re playing against a combo or control deck, then it probably is, as our own life total would be close to irrelevant and any small boost in the number of expected spells helps. But if we’re playing against another aggro deck, then it probably isn’t, as that single point of life may make all the difference in a damage race. So it’s all dependent on the matchup.

Another thing to consider is how many cards you expect to draw in any given game. If you’re playing a high-velocity deck that tries to draw a lot of cards, then you may see a large portion of your library in any given game, at which point the fractional extra spell might be worth the life cost.

If you want a general guideline answer, then I would say that one card is worth four points of life, either paid or gained. In some matchups it will be more, in some matchups it will be less, but this 4:1 exchange is based on Sylvan Library. It’s also seen on Ojutai’s Command and Demonic Pact if you consider all non-losing options to be of equal value. And it’s the same card-life exchange in escalating Collective Brutality. If you agree that 4 life = 1 card, which implies that 1 life = 0.25 card, then the above chart shows that you need to draw 22 cards before you’ve recouped your investment, at least in the specific scenario I set up under my assumptions.

And 22 draws is a lot. While there are Modern decks that sift through half of their library in an average game, these decks are rare. For most decks and matchups, playing Prismatic Vista with the sole purpose of thinning your deck is not worth it, as the price of paying 1 life usually exceeds the benefit gained.

Yet there are exceptions, and one way or another, fetching to fix your mana remains worth it. I expect that Prismatic Vista will be one of the most sought-after cards from Modern Horizons.

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