These allow users to complete specific challenges to earn in-game rewards like special promotional cards, various cosmetic items, and even (at times) packs for players to open
You can obtain the Cloyster (1-Star Shiny rarity) card by opening Crimson Blaze from Crimson Blaze set
Card Value Scanner is built around that full workflow, while tools like TCGplayer, PriceCharting, Cardmarket, Collectr, and Pokellector can be useful supporting references depending on whether you need marketplace pricing, historical sales, European pricing, collection tracking, or set browsing
For some people, it's the game play, the back and forth of building an army of creatures and slamming them into each other to see who is stronger
On the former, I really value raw battlefield presence in a deck like this