Players may know by now that there’s a much higher Shiny rate in Pokémon Legends: Arceus than other games in the series, but the new Daybreak update has added a mode that also has an increased Shiny rate. To start these events, one must first complete a questline that ends with a quest called “Daybreak.” Once completed, players will experience large herds of Pokémon traveling around the landscape during rainstorms and snowstorms. The Shiny rates are less than those of regular Mass Outbreaks, but still better than simply exploring the different areas of Legends: Arceus.
In Brilliant Diamond and Shining Pearl, for example, about every 1 in 4096 Pokémon will be a Shiny variant. During regular gameplay and without a completed Pokédex entry, Pokémon Legends: Arceus, has exactly the same drop rate. Regular randomized Mass Outbreaks during the game have drastically increased odds – 26 in 4096 or 1 in 158.2, and with a level 10 Pokédex entry and a Shiny Charm, those odds jump slightly higher to 30 in 4096.
Massive Mass Outbreaks have been programmed to have a lower Shiny rate as a lot of Pokémon appear during these events. Different hordes of Pokémon will appear across the map, so even with a lower spawn rate, Shiny grinding in an area with a rainstorm and an Outbreak is worth it. Still, for people that are experiencing the Massive Mass Outbreaks casually, there’s a real possibility to find and catch a Shiny Pokémon. Just like the odds in the rest of the game, the chances of finding a Shiny Pokémon in Arceus' Mass Outbreaks increase slightly with a perfect Pokédex entry and using the Shiny Charm.
Pokémon Legends: Arceus' Massive Mass Outbreaks Shiny Rates
According to Serebii.net, Massive Mass Outbreaks in Pokémon Legends: Arceus have basic Shiny odds of 13 in 4096. The scaling on Shiny percentages is also worse than Mass Outbreaks, moving to 16 in 4096 with a perfect Pokédex entry, and using a Shiny Charm with a perfect Pokédex entry puts the odds at 19 in 4096. This means the best percentage chance of getting a shiny is 0.4% while during a Massive Mass Outbreak, but this is an improvement over the 0.02% chance of finding an isolated Shiny in the wild.
If a star symbol is next to a Pokémon's picture on the map where the Massive Mass Outbreak is taking place, that encounter will be a Special Outbreak. Special Outbreaks in Legends: Arceus are followed up by another influx of Pokémon that can either be an evolution or Alpha versions. The Shiny percentages don't seem to change based on whether or not it is the first wave or second wave of an outbreak, so finding Shiny evolutions and Alphas can be easier during a Massive Mass Outbreak.
Although Massive Mass Outbreaks in Legends: Arceus can happen in every area, and many different types of Pokémon can be found during the event, it doesn’t change the Pokémon that can appear. Pokémon Legends: Arceus also randomizes how many Pokémon actually appear during a Mass Outbreak, so whether players should go after Mass Outbreaks or Massive Mass Outbreaks is yet to be determined. Regardless, the increased Shiny rates still make finding Alphas easier and a time saver for those grinding toward finding multiples.
Source: Serebii