The Max Charm is one item that was revealed when the Isle of Armor was first announced. Instead, it is one of the very few things that were a surprise for players to discover when playing. The Mark Charm is different from previous Charm Items in that it increases the chances of Wild Pokemon that are captured having special Marks.
If you don't recall, Marks are randomly found on Wild Pokemon. Though they don't bring along any competitive advantage, they are very rare on any Pokemon (sort of like how Shiny Pokemon are extremely uncommon but have no special differences). Marks are similar to Ribbons in that they appear on the status screen of a Pokemon's Profile Page. Just like ribbons, players have the ability to attach marks to the Pokemon that has them. When sent into battle, Pokemon with assigned marks will have a special tagline said indicative to the Pokemon Mark.
In order to obtain the Mark Charm, one must catch every single Pokemon found within the Isle of Armor (minus Zarude). That's a whopping 210 Pokemon that must be captured in order to receive the Mark Charm from the Professor within the Train Station! But there's a catch: a player must catch all of the Pokemon on the Isle of Armor. Any Pokemon transferred from Pokemon HOME will not be added to the Isle of Armor Pokedex, meaning you literally have to catch every single Pokemon found on the Isle of Armor in order to obtain the Mark Charm. It's certainly a task, but it's one that is well worth it if you are looking to increase the likelihood of finding Pokemon with Marks. It's sort of like how the Shiny Charm helps with Shiny Pokemon Hunting - it all depends on the player and if it's worth it to them!
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