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1. Having an up to date living dex that is put into Bank and used for Breeding/Pokédex purposes. A Masters work is never done, since new Pokémon will be discovered each gen, but being able to have a complete Pokédex each generation with ease is the mark of a master
2. Have a team of YOUR OWN Pokémon with the Champion Ribbon of at least ONE League signifying that you have mastered a regions rigourous battle requirement and came out on top. The more you have, the more you are considered a Masterful trainer.
3. Have at least 1 of YOUR OWN Pokémon with a Battle Facility Ribbon. One proves that you had what it takes to take on at least a singular Frontier trainer, and the more you have the better reason to call you a Master.
4. If there's a side Facility like Contest Halls or Battle Royale, have at least one of your own Pokémon hit Master level and recieve the respective Ribbons. A Master must be skillfull in things other than battle.
5. Breed your own multi-IV Pokémon
and raise them to take on other trainers without using PKHEX. If you can beat cheaters even more of a reason to be called a Master.
5. Obtain at least one LEGITIMATE shiny Pokémon through catching or hatching. This is a rite of passage into really putting maximum effort into getting something not many people can get their hands on legitimately. The more legitimate shinies, the more of a Master you are deemed. Events don't count.
6. Clear the trials of at least one other non-mainline game to get Pokémon/Ribbons that you can't normally get. Specifically stuff like becoming a Pokémon Ranger and getting a Manaphy egg as proof or softening the heart of a shadow Pokémon to get a National Ribbon. Masters must be flexible in their adventuring and be open to new and different roles. Bonus points for anyone who has a legit Hayley Mew or a legit Purified Lugia. Stuff like beating Pokémon Snap or Stadium or even being really good at the TCG is kinda tertiary but lends credence to your love of Pokémon.