Is This The Rarest Pokémon Ever Caught?

This is a Larvitar. There are many like it, but this one is mine. Actually, no, there aren't many like it. In fact, I'd be surprised if there were any others like it at all.

This Larvitar has two primary characteristics that factor into this assertion: it is Shiny and possesses the Sandstorm Mark. It is possibly the rarest Pokémon I will ever collect. It may be one of the rarest Pokémon anyone will ever collect. Why is that? Let me explain.

What is a "Shiny"?

Ever since Gold and Silver in 1999, Pokémon have had a chance to appear with an alternative color palette. The term derives from the sparkling "shine" animation that plays when the Pokémon hits the field. As you might have gleaned from the title of this article, they're rare! In the modern generation of games, wild Pokémon have a 1/4096 chance of being Shiny, which are actually much better odds than were present when the mechanic was introduced!

This Larvitar is a darker shade of green than normal. He will evolve into a sandy-colored Tyranitar.

Additionally, long-time players might also know that there's a trick known as the "Masuda Method" that can drastically increase the odds of hatched Pokémon being Shiny. It simply involves breeding two Pokémon who originated from games with different language settings, and increases the Shiny odds sixfold; up to 6/4096, or 1/683. This is typically considered the easiest and most reliable way to obtain a shiny Pokémon, but unfortunately, is not a method we can leverage, for reasons that will be explained momentarily.

What is a "Mark"?

Starting with Sword and Shield in 2019, wild Pokémon may have a badge applied to them when they spawn, known as a "Mark". Marks are extremely similar to Ribbons, except that they (typically) can't be earned, only found. In fact, only wild Pokémon can have a mark; hatched Pokémon will never have one (thus, the aformentjoned "Masuda Method" goes out the window). This provides an incentive towards actually catching your monsters instead of just breeding in the post-game. It's a nice bit of style.

Marks, like Ribbons, can be "equipped" on the status screen to give your Pokémon a unique title when being sent out. Fans of the channel will recall that I went to great lengths to collect every Ribbon on my Torkoal for this very reason. In this case, our Sandstorm Mark bestows the title "the Sandswept", which I feel is particularly apt for what will eventually be a Tyranitar, a Pokémon famous for summoning a sandstorm when it enters battle.

Equipping a Mark on the status screen (displayed here on my English save file for your convenience).

Marks, like Shinies, are also rare, though less so. There are several categories of Mark, each with different odds of appearing. The rarest Mark in the game is the aptly-named "Rare Mark", which has a 1/1000 chance of appearing on any given wild Pokémon. The Sandstorm Mark falls under the category of "weather marks", which only roll their odds on Pokémon that spawned while a certain weather condition is occurring in the overworld. In this Mark's case, it's a 1/50 chance that any wild Pokémon will have it, if the current weather is a sandstorm.

Quick Math

So! We have a Shiny Pokémon that has a Mark, meaning that it had to be caught in the wild, eliminating the possibility of us leveraging the improved odds of the "Masuda Method".

The math is pretty straightforward, with two sets of odds that are independent rolls: 1/4096 * 1/50, which comes out to a nice 1/204800, or a ~0.0004% chance of encountering a single Pokémon with both of these characteristics (assuming the encounter occurred during a sandstorm, which itself is also randomly-occurring, with odds that I don't have numbers for).

More Than The Sum Of Its Parts

But wait! "Tom!", you say, "You just told us that there was a Mark with 1/1000 odds! Wouldn't a Shiny with that Mark be the rarest Pokémon you could obtain?" And under normal circumstances, I think you'd be right. But there's an additional, less-tangible factor in this equation which I haven't told you about yet: ironically enough, Larvitar does not spawn in any location where sandstorms occur.

So how did I find this Pokémon without modifying the game code?

In Scarlet and Violet, there are periodic events known as "Mass Outbreaks", which run for about a week and are activated when your Switch logs in to online services. These events cause Pokémon of a given species to spawn in huge quantities at random locations in the overworld. Do you see where I'm going here?

Between August 23rd, 2024, and September 1st, 2024, an event rolled out which enabled Mass Outbreaks for Bagon and Larvitar. This meant that, for the first time, it was possible to encounter Larvitar in the Asado Desert, which is the only location in Scarlet and Violet where sandstorms happen.

A Larvitar outbreak occuring in the Asado Desert, indicated on the map.

And do note that I only say "possible"; the location of these outbreaks changed every day, and lasted for the whole day. Therefore, it would be entirely likely for any given player to have played the game every day for the complete duration of the event, and still never have been given an opportunity to encounter Larvitar in the desert. That's rough!

Fortunately (for me), if you don't sign back in to online after the event ends, your console doesn't get the memo and continues the event until you do. As such, I was able to wait until I got my lucky Mass Outbreak location, well after the event should have ended.

Given infinite time, one would eventually be able to reproduce the odds of finding a Shiny Larvitar with the Rare Mark. The same cannot be said for a Shiny Larvitar with the Sandstorm Mark. Assuming the Switch logged into online services after September 1st, 2024, thereby ending the event, it does not matter how much time you spend; you will never find another Shiny Larvitar with the Sandstorm Mark, because Larvitar will stop spawning where sandstorms occur. Therefore, I posit that this makes my Larvitar one of the rarest Pokémon of all time, as a finite number of them will ever exist.

TL;DR

Anyway, all this digital ink spilled to say that I'm very happy that after 5 years of Marks being added to these games, I was finally able to obtain the Sandstorm Mark on the sandstorm Pokémon.

Oh! And here's a video of me catching the guy, just to prove I actually did.

Thanks for reading.