The Pokémon Terastal Festival ex High Class Booster Pack is part of the Pokémon Trading Card Game (TCG) expansion that features the Terastal mechanic introduced in the Pokémon Scarlet and Violet games. This special set focuses on the Terastal phenomenon, where Pokémon can change their type and gain a shimmering crystal-like appearance. The pack typically includes a collection of powerful cards, many featuring Pokémon ex, which are stronger versions of Pokémon cards with unique abilities.

Key highlights of the Terastal Festival ex High Class Booster Pack include:

1. Terastal Ex Pokémon: The set showcases Terastal versions of various Pokémon with new designs and enhanced stats, offering a dynamic gameplay experience.
2. High-Class Cards: As a high-class pack, it contains rare and powerful cards, including full-art cards, trainer cards, and other special variants designed to enhance the collection for both players and collectors.
3. Special Artwork: The cards often feature elaborate and colorful artwork, with some showcasing Pokémon in their Terastal forms, which shine with crystal-like effects.
4. Rare and Collectible: The packs include special rare cards like Full-Art, Secret Rares, and other special versions, making them highly sought after by collectors.

The Terastal Festival ex High Class Booster Pack is typically released as a limited edition, and it's part of a broader effort to introduce players to the new Terastal mechanics and enhance their deck-building options.