These were the cards that shaped the tournament, that sparked discussions and were the most debated, the cards that won games and turned Grand Prix Kraków into an event to remember ...
Foul-Tongue Invocation may have been the most important removal spell of the tournament. The ability to even touch an untapped Dragonlord Ojutai (which turned out to be quite important itself) or a Silumgar, the Drifting Death proved crucial in the control mirror match. And that was the most-played matchup in the Top 8, with four of seven matches featuring Silumgar's Scorn, various Dragons, and, of course, Foul-Tongue Invocations.
Mastery of the Unseen
Mastery of the Unseen was one of the few cards to allow players to combat the ubiquitous Esper Dragon deck. Especially in combination with Deathmist Raptor and Den Protector, as seen in Sam Pardee's Top 8 deck built by Craig Wescoe, the card did its fair share of work. Despite the lack of Perilous Vault in any of the control decks, and thus no option to get rid of the enchantment once resolved, Pardee fell in the quarterfinals; but Mastery of the Unseen will have ample opportunity in coming weeks to take revenge.
Haven of the Spirit Dragon
Kraków itself proved to be a safe haven for the Spirit Dragon. As has been mentioned before and will be mentioned again, Ugin and his more creature-typecast Dragon friends had one of the best weekends of their thousand year-long existence here. To have a land which could trade itself in for a big threat was a boon to Dragon decks everywhere; that it helped with the splash of Dragonlord Ojutai on top of that was more than just a nice bonus!
Dig Through Time
"The overarching theme of the matchup was card draw effects quickly snowballing out of control," Hall of Famer and fellow coverage reporter Frank Karsten summed up the final match of the day between Robin Dolar and eventual champion Alexander Hayne. "Thoughout the final, we kept track of a metric we called succesful DPA which stands for succesful resolutions of Dig Through Time per attempt. Hayne came out ahead and indeed won the match."
Dragonlord Ojutai was called the most important card in the Top 8 by … well, basically by the Top 8, as a full four of them listed the mighty Dragon as such. Hall of Famer Paulo Vitor Damo da Rosa in particular stressed the importance of being able to take a more proactive role in certain matchups. Dragonlord Ojutai did that, and its influence wasn't limited to the ubiquitous Esper Dragon deck either. Sam Pardee was one of the few players in the Top 8 who didn't run the deck, but he still included Dragonlord Ojutai in his otherwise green-white build.