Designing a great Magic deck requires comprehension of what cards you will face. To make this manageable and unique, the Standard format only allows recently-printed cards: something like 1000-1500 cards at a time. Standard is one of Magic's more popular formats and most Pro Tours focus on it.
Standard rotation is staggered such that sets enter the format more often than sets leave. Each new set is legal immediately, and then every October, four sets leave as the next one joins the four that remain.
In the past, changes in the meta-game usually occurred when sets rotated out. Recently, however, Wizards has found ways to balance powerful cards with appropriate drawbacks, so there are increasingly diverse strategies.
At Pro Tour Eldritch Moon, many cards from the new set were featured in successful decks (there were 13 Eldritch Moon cards in the top 8 decks — almost like one of the Gothic horror references in the set). The new mechanics, designed to show the evolution and emergence of new beings that had been the cause of increasing madness and delerium on the planet, were good enough to beat back the reigning staple, Collected Company, and the final match ended in a showdown between the set’s hero, Liliana, and its villain, Emrakul. It was a thrill to watch and quickly created interest in those cards.
The following Pro Tour final was a different sort of thrill: an endurance match between two forms of control decks that shifted gears every few minutes, becoming a master class in the mathematical techniques that pros have developed over the years to lock each other down. When Brian David-Marshall, the Pro Tour historian, asked Shota Yasooka for advice to those who would copy his winning deck, Shota hilariously deadpanned “Don’t”. I think he was saying that the meta-game would quickly shift, and also that the skill required to make it win was more complex than it looked. Incredibly, he had intuitively assembled it the night before, informed by his years of top-level play.
The next season, after Emrakul was actually banned because of being too dominant, Pro Tour Aether Revolt ended with six very similar decks of the “Mardu Vehicles” aggro archetype, suggesting that the mechanics created for this block were too over-powered to exist on a level playing field of the sort that makes the skill of Magic pros roughly as important as their chosen deck.
No one knows how Pro Tours will end — there’s just too many geniuses in the room, and too many cards in the pool. Wizards’ R&D department plays thousands of matches to make sure cards are well-balanced in the meta-game, but they are not as good as the pros at breaking (or solving) a format.
The Pro Tour has lots of familiar faces among it’s ~400 entrants, but most of them can capably shift from one archetype to another — so it’s fun to guess what type of deck everyone will bring.