>>41510569Shiny chance inherently increases for all encounters of a specific species when you reach a certain number of that species where you completed the battle (either by KOing it or capturing it).
At 50 encounters you have 2x chance (1/2048)
At 100 encounters you have 3x chance (1/1365~)
At 200 encounters you have 4x chance (1/1024)
At 300 encounters you have 5x chance (1/819~)
At 500 enouncters you have 6x chance (1/682~)
Shiny charm adds an additive 2x to this
So shiny charm + 50 encounters = (2 + 2)x chance, or 4x chance.
Shiny charm + 500 encounters = (6 + 2)x chance, or 8x chance (1/512).
The Pokedex keeps track of how many of each species you've battled. Trainer battles count. I'm not sure if Battle Tower does, anyone know?