Pokémon Legends: Arceus — Ultimate Mass Outbreak guide

Mass Outbreak Pokemon Legends Arceus Three Stunky
Mass Outbreak Pokemon Legends Arceus Three Stunky (Image credit: iMore)

There are several new mechanics and ways of catching Pokémon in Legends: Arceus making it one of the best Pokémon games to ever release. Perhaps the best new mechanic revolves around Mass Outbreaks, which is when several Pokémon of a particular species spawn on repeat for a short period. Turns out, your chances of catching a shiny Pokémon during a Mass Outbreak go up significantly as well. I have already caught four shiny Pokémon thanks to Mass Outbreaks. There's a lot to go over, so let's dive in.

What is a Mass Outbreak?

Pokemon Legends Arceus Mass Outbreak Map (Image credit: iMore)

Within Pokémon Legends: Arceus, a Mass Outbreak is when one Pokémon species spawns repeatedly in an area for a short amount of time. You can tell there's a Mass Outbreak if you see a circle on the map with a Pokemon's face in it. During this window, your chances of encountering a shiny Pokémon for that species increases significantly if you are in the Mass Outbreak area. The shiny odds are even more in your favor if you've worked on that Pokémon's Pokédex entry.

This fun new mechanic has kept the game interesting for me long after beating the main storyline, which has helped make this one of the best Pokémon games of all time.

What to do during a Mass Outbreak

Pokemon Legends Arceus Mass Outbreak Discovered (Image credit: iMore)

If you see a Mass Outbreak symbol on the world map, you should make sure you have plenty of Poké Balls on you and then head towards it right away since they don't last very long. I've seen four shiny Pokémon during my playthrough so far, and most of them have appeared during Mass Outbreaks, specifically when I attempt to catch the Pokémon rather than fight them. More Pokémon will spawn to take their place, making it possible for a shiny to appear.

If multiple Mass Outbreaks are available, I suggest going for whichever one you have a higher Dex entry for, as this increases your shiny chances (more on that to come). Or just go for the Pokémon that you like better.

  • Carefree Pokémon: Pokémon like Bidoof are the easiest to catch during a Mass Outbreak. Just go nearby and start hurling your best Poké Balls at them repeatedly. The more you catch, the more will spawn, increasing your shiny chances. Regular Poké Balls or Great Balls are a good choice here.
  • Skittish Pokémon: Hide in tall grass and repeatedly chuck Poké Balls at the Mass Outbreak without being seen. Feather Balls, Wing Balls, and Jet Balls are your friends here since they can be thrown very far, allowing you to maintain your cover.
  • Aggressive Pokémon: Make sure you have plenty of stunning items like Balls of Mud, Spoiled Apricorns, or Snow Balls. Go somewhere out of reach and chuck Poké Balls at the Mass Outbreak. If a Pokémon attacks, throw a stunning item at it and attempt to catch it. If you faint, you might be able to travel back to the Mass Outbreak and keep catching Pokémon before the event ends. You'll want to use more heavy-duty Ultra Balls or the like to capture these guys.

After a while, a notification will appear on the screen telling you, "The reported Pokémon seem to be gone..." which signifies that the Mass Outbreak has ended.

Mass Outbreak shiny odds

Shiny Misdreavus Pokemon Legends Arceus (Image credit: iMore)

Your base shiny odds when you start the game are 1:4096. However, if you have gotten a Pokédex entry up to level 10 for a specific Pokémon when it has a Mass Outbreak, those odds increase to roughly 1:819.6. You can even increase those odds to 1:128.49 if you have completely filled out the Pokédex entry for that Pokémon, which means there are red checkmarks next to all of the possible research tasks, it will result in stars appearing around the Poké Ball icon.

Swipe to scroll horizontally
NameRateW/ Shiny Charm
Base Rate1:4096--
Dex Level 101:2048.251:819.6
Complete Dex1:1024.381:585.58
Mass Outbreaks1:158.02--
Dex Lvl 10 & Mass Outbreak1:152.191:137.02
Complete Dex & Mass Outbreak1:141.721: 128.49

How to trigger a Mass Outbreak

Pokemon Legends Arceus Mass Outbreak Icons (Image credit: iMore)

As far as we can tell, Mass Outbreaks pop up at random. However, you are more likely to trigger one if you travel between locations. So, for instance, travel to Obsidian Field, then travel back to Jublife Village and check the map to see if anything has spawned. If nothing has, travel somewhere, then return to Jubilife Village and recheck the map.

Take on the mob

Mass Outbreaks are a brand new mechanic first seen in Pokémon Legends: Arceus. They allow players to capture many Pokémon of the same species and can increase your chances of catching a shiny Pokémon. They keep the game exciting far after the main storyline has been completed.

Good luck with your Mass Outbreak hunting. I hope you can catch several shinies using this new mechanic.

Rebecca Spear
Gaming Editor

Gaming aficionado Rebecca Spear is iMore's dedicated gaming editor with a focus on Nintendo Switch and iOS gaming. You’ll never catch her without her Switch or her iPad Air handy. If you’ve got a question about Pokémon, The Legend of Zelda, or just about any other Nintendo series check out her guides to help you out. Rebecca has written thousands of articles in the last six years including hundreds of extensive gaming guides, previews, and reviews for both Switch and Apple Arcade. She also loves checking out new gaming accessories like iPhone controllers and has her ear to the ground when it comes to covering the next big trend.