* Master Balls are rare items: Master Balls are extremely rare in most Pokémon games and are not typically earned through training.
* Regis and level-up rewards: The Regis (Regirock, Regice, Registeel) don't have any special rewards associated with reaching level 100, including Master Balls.
How to obtain Master Balls:
* Events: Some games offer Master Balls as event rewards.
* Trading: You can obtain Master Balls by trading with other players.
* Cheating: Some methods exist to get Master Balls through game glitches or hacking, but these are not legitimate ways to obtain them.
Let me know if you have any other Pokémon questions!