The "Mask of Change" set in the Pokémon Trading Card Game is centered around the debut of Ogerpon, a legendary Pokémon with the ability to change its type by wearing different masks, making it a key feature of the set; it includes various "Mask Ogerpon" cards with unique abilities depending on the mask they wear, alongside other new characters and cards, often with themes of transformation and strategy based on different mask powers. 
 
Key points about the "Mask of Change" set:
 
Main focus on Ogerpon:
The set prominently features Ogerpon in different mask forms, with each mask granting different type and attack capabilities.
Type-changing mechanic:
The core theme of the set revolves around Ogerpon's ability to change its type by switching masks, allowing for diverse gameplay strategies.
New characters and cards:
Besides Ogerpon, the set introduces new characters and supporting cards that might also have mask-related abilities or themes.
Potential for deck customization:
With multiple Ogerpon variations and supporting cards, players can build decks focused on utilizing different mask combinations to adapt to various match-ups