In a tournament, what factor does a "Constructed" format primarily involve?

In a Constructed format, the defining characteristic is that players compete using decks that they have built outside the tournament, prior to the event itself. Participants select cards from their entire collection or from a specified card pool based on the format's rules, such as Standard, Modern, or Legacy. This allows players to strategize and customize their decks to reflect their preferred playing style and tactics, making deckbuilding a crucial element of the experience.

The focus of Constructed formats is on the player's ability to create a cohesive and effective deck, whereas the other options pertain to different aspects of gameplay or alternative formats. For example, building decks from a limited pool of cards is central to Limited formats, and sealed packs imply a gameplay scenario distinct from Constructed. Additionally, pairing teams against each other refers to match organization rather than the deck construction process. Therefore, the correct answer accurately captures the essence of what a Constructed format entails.