You don’t necessarily have to “do” anything to unlock Mass Outbreak (though we’ll talk about a few ways you can exploit this system in a bit). Instead, they will happen randomly as you play the game. You should be able to spot an area by scrolling between the different areas of your map and looking for the “Mass Explosion” message in the top left. From there, you can simply tour typical Pokémon hotspots and see if you’re lucky enough to find more creatures than usual. In addition, the gatekeeper at Jubilife Village will let you know when there is an outbreak of disease.
There’s no word on the official “occurrence rates” of these Mass Outbreaks, but it’s pretty clear at this point that some players seem to be experiencing them more often than others. It seems like beating the main questline will increase your chances of one, but there’s a chance that Mass Explosions happen before that.
Pokémon Legends Arceus: How do you catch more shiny Pokémon during mass outbreaks?
Interestingly, it turns out that mass outbreaks increase the spawn rate of shiny versions of Pokémon affected by them. While it was initially believed that your increased chance of finding shiny Pokémon during the Mass Outbreak was simply based on the fact that there are more Pokémon to find in them (and that could be a part of the equation), but it seems that Mass Outbreaks also naturally increase the spawn rate of Shiny Pokémon.
To hunt shiny Pokémon during mass outbreaks, you really just have to join them. The exact odds of finding one are currently being calculated, but one of the more common estimates I’ve heard floating around is that you can find a shiny Pokémon in at least one of them. 10 Mass Outbreaks You’re In. A bit of Actual Playtime seems to confirm that the estimate is at least almost accurate, but the bigger take here should assume that Mass Outbreaks are your best chance to hunt for shiny Pokémon .
Pokémon Legends Arceus: How do you trigger a mass outbreak?
The bad news is that there is no specific way to trigger a Mass Outbreak. That means there doesn’t seem to be a magical set of inputs you can use to start a Mass Outbreak out of nowhere at the moment.
However, there is a way to increase the odds you encounter. If Mass Explosion does not occur, go to any area on the map and then return to Jubilife Village. This effectively “resets” the map, which also means it resets the chance for a Mass Boom to happen. You’re still depending on the normal odds of a naturally occurring Mass Boom (low and chaotic), but if you’re looking for shiny Pokémon, this is a great way to maximize your play time.
https://www.denofgeek.com/tv/pokemon-legends-arceus-mass-outbreaks-explained-shiny-pokemon-odds-list/ Pokémon Legends Arceus: How to Use Mass Outbreaks to Catch Shiny Pokémon