As their name suggests, Massive Mass Outbreaks are Mass Outbreaks but on a far bigger scale. When one of these occurs, around a dozen outbreaks will appear simultaneously.
How to Trigger Massive Mass Outbreaks
These special Mass Outbreaks will only start appearing after accepting Request 96, which is only available during the postgame and after downloading the latest software update (1.1.0 or higher).
Just like regular Mass Outbreaks, each time you return to Jubilife Village there’s a chance that a Massive Mass Outbreak will occur in one or more regions. Therefore, you can simply keep leaving and returning to the village until one appears.
How Massive Mass Outbreaks Work
In contrast to normal Mass Outbreaks, you cannot see what Pokémon appear in each individual outbreak–at the beginning anyway. On the map, each outbreak will show up as a question mark icon. To learn what Pokémon’s in the outbreak, you must physically be near the outbreak.
Another key difference: there is a hard time limit for the Massive Mass Outbreak. When the rainstorm or snowstorm ends, all inactive outbreaks will vanish and (if you’re at one) the active outbreak will stop spawning new Pokémon. From time to time, there will be a message along the top of the screen indicating roughly how much time is left.
Unlike regular outbreaks, evolved versions of the Pokémon can also spawn. Eg. Dartrix in a Rowlet outbreak. Additionally, after clearing out an individual outbreak, there’s a small chance that a second wave will spawn in the same location. This second wave will feature either evolved versions of the first wave or all alphas.
Finally, not all outbreaks are equal. You may notice some outbreaks have a glowing border and an icon next to it–these are special outbreaks.
- A star icon means that outbreak will always have a second wave. As mentioned above, the second wave may include evolved versions of the original wave or all alphas.
- A berry icon means that you can acquire Aguav Berries from that outbreak. These can be given to Mai’s Munchlax to reveal all of the outbreak Pokémon on the map. So you don’t need to guess.
Benefits of Massive Mass Outbreaks
The most obvious benefit of Massive Mass Outbreaks is that it’s easier to encounter certain rare Pokémon–and alpha versions of them. For example, the Hisuian starter Pokémon (Rowlet, Cyndaquil and Oshawott) are fairly common during Massive Mass Outbreaks.
Regarding alphas, as mentioned, some outbreaks (with a shiny star icon) have a guaranteed chance of featuring a second wave–and this second wave may be all alphas. Therefore, using our previous example, you could be lucky and find an outbreak with all alpha Rowlets.
Lastly, the shiny rate during Massive Mass Outbreaks is much higher than normal, but lower than regular Mass Outbreaks: 1 in 315 versus 1 in 158 (not counting boosts from the Shiny Charm or Research Task progress). Overall, the trade off is generally better, since you can encounter a wider selection of Pokémon. However, if your favorite Pokémon appears in a normal Mass Outbreak, you should go there instead.
(Numerical data via @Sibuna_Switch)