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 Seville into an event to remember...
While Fate Reforged's many spicy additions to the format were the talk of the tournament, it obviously wasn't all new here. One of the old favorites of Standard in particular, Siege Rhino, simply couldn't be killed. Or rather, it could be killed and often was, but then the Rhino had done half its job already; life was lost and gained, and sometimes Siege Rhinos don't die after all and instead smash faces. The card played a huge role in getting Nicholas Merrien and Pierre Sommen all the way to the semifinals and finals, respectively, of this Grand Prix, even if other cards prevailed in the end.
Shaman of the Great Hunt
Shaman of the Great Hunt is just so, so versatile. It offers a sizeable threat in its own right, at times it can generate nontrivial amounts of extra cards, it quickly turns a bunch of token creatures into a serious strike force … No wonder so many different deck archetypes employed the Shaman to make hunt at this Grand Prix! The card made appearances virtually everywhere, from Temur, of course, to Red/Green Beatdown, but also in quite a few Jeskai decks where it combined well with tokens provided by Raise the Alarm, Hordeling Outburst, and/or Monastery Mentor.
"The card is like a Planeswalker you can't kill with damage!" None other than No. 19 Martin Jůza was singing Outpost Siege's praises even during the early rounds of Saturday. He considered it one of the sleeper cards of the new set and suggested that people might want to pick it up before someone went and won a Grand Prix with it. While that didn't happen this weekend, as Jůza "only" made it to the Top 8 (the 22nd of his career), one can't really discount those comments. So yes, there's still time. Before someone really goes and wins a Grand Prix with it.
Crux of Fate
From time immemorial, access to an efficient mass removal spell has been the crux of control strategies. Handling the opponent's threats one by one is all fine and fair, especially when backed up by other sources of card advantage, but sometimes one really needs to be unfair and wipe away all of the opposing offense in one big swipe. Crux of Fate does exactly this and has led to a resurgence of blue-black or Sultai control decks. The card's influence on the format goes beyond that, however, as demonstrated by the emergence of red-white or red-green beatdown decks at this event which specifically include Stormbreath Dragon to counteract Crux of Fate's effectiveness, just like the control players themselves often run Silumgar, the Drifting Death to stick around past Crux of Fate.
Ugin, the Spirit Dragon
Eight mana is a lot. But the huge colorless Dragon Planeswalker appears to be worth all of it, and has found a home in virtually every single archetype that can realistically expect to cast him, whether it's control decks waiting for the later stages of games or Frontier Siege and/or Nykthos, Shrine to Nyx-powered ramp strategies. Many players have erroneously considered him "just another big finisher," when Ugin is in fact so much more than that. Time and again over the course of the weekend, we've seen players in seemingly unwinnable situations topdeck Ugin to wipe the board and retain a formidable threat of their own. Ugin doesn't turn tables; he upends them. No wonder eventual champion Immanuel Gerschenson called him the most important card in his deck.