Wurmple will evolve into either Silcoon or Cascoon. However, this is determined by Wurmple’s Encryption Constant, which is a hidden factor that players cannot see. From your perspective, Wurmple’s evolution will seem to be random—even though it’s not.
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How Encryption Constants Affect Wurmple’s Evolution
Personality Values affect a few things in Pokémon Legends: Arceus (and many things in past games). In addition to determining the overall size of a Pokémon, it also affects some species-specific factors. A newer addition to the Personality Values mechanic is the Encryption Constant.
For Wurmple, the Encryption Constant affects whether it evolves into Silcoon or Cascoon. Interestingly, this is the only Pokémon that has its evolution determined in this way.
An Encryption Constant is a string of four eight-digit numbers in a row. Overall, there are 32 digits in this string. The first half (the first 16 digits) of the Encryption Constant is used in an equation. This equation is the 16-digit number run through a Modulo Operation involving the number 10.
If, after this equation, the value is less than or equal to four, Wurmple will turn into a Silcoon when reaching level seven. If the result is greater than four, Wurmple will turn into a Cascoon.
What Determines a Pokémon’s Encryption Constant
It’s random. The game gives this value to a Pokémon using a generator. Furthermore, you won’t be able to tell. The Pokémon games never make this data available to the player.
As such, you can’t predict whether your Wurmple will become a Silcoon or Cascoon. Thankfully, in many games, you can straight-up catch Silcoons and Cascoons. This removes the need to evolve Wurmple in the first place.
How Modulo Operations Work
Basically, this is a way some computing systems make random things not-so-random. A Modulo Operation takes two numbers and sees how many times the second one fits into the first. Afterward, the system uses the remaining value. The equation is often written as “[first number] mod [second number].”
For example, if we do 5 mod 2, we’ll get a 1 as a remaining value. This is because 2 fits into 5 twice, but leaves a 1 as a result.
In terms of the equation that determines how Wurmple evolves, this would be “[the 16-digit number of the first half of Wurmple’s Encryption Constant] mod 10.”
You would think that 10 can fit into a 16-digit number quite a lot, and therefore make Wurmple evolve into Cascoon more often. However, you need to keep in mind that this 16-digit number can begin with any number of 0s.
Why This Matters
Well…technically, it doesn’t. There’s no way you can see a Pokémon’s Encryption Constant in-game. Furthermore, you can’t do anything to change it. So, even if you did find a way to see this data, you wouldn’t be able to change it unless you hack the game.
However, it can be interesting to take a look at these mechanics. There’s no reason that Wurmple’s evolution should be this complicated. But that’s the thing—it’s a product of past coding.
Prior to Encryption Constants being part of the games, Personality Values were used. On top of that, they were used for a ton of other things. The shiny calculation, gender, and much more used the Personality Value system to determine what a Pokémon would be.
How Wurmple evolves is an artifact of how things happened in the past. It remains as a testament to previous coding strategies used by the developers.
In the future, this mechanic may change. Developers are always improving their games and codes. For now, let’s just enjoy these small reminders of where the Pokémon games came from.