In 2011, the Magic: The Gathering storyline was in the with the Scars of Mirrodin block and story arc, which brought back the Phyrexians (albeit, a new breed of Phyrexians) as the big villains at the time.
Basically, the storyline dealt with who was going to take control of the Mirrodin Plane - the Phyrexians or the native Mirrans.
Not wanting to spoil how the ending went in the last expansion of the block (including which side of the struggle would prove victorious), Wizards of the Coast devised two set concepts: Mirrodin Pure and New Phyexia. In short, they did this because they didn't want anyone to know beforehand how things were going to shake out.
Well, spoiler alert, the Phyrexians won. As such, the set was called New Phyrexia complete with a Phyrexian symbol as the set's expansion logo. And that's despite a small leak at the time that spoiled the outcome for some players. Still, a lot of people thought that the Mirrans were going to win and, when it went the other way, it still somewhat surprising for some people.
And that was it right? No hint at what a Mirran victory would be like?
Well, there is a single card printed that stems from a Mirran victory over the Phyrexians and a would-be Mirrodin Pure outcome.
Complete with it's own unique set symbol, this card was just a taste of what the expansion could have been like if Magic went the other way on who won. That card? Pristine Talisman.
It was released during New Phyrexia's predecessor, Mirrodin Beseiged's Game Day event, and, honestly, it's a bit underwhelming of a card.
It's a three-costed mana rock that can only provide colorless mana. At least it also gains you one life each time it's used. Really, it's not all that amazing, but it highlighted the emphasis on life and light in a set that was very much the opposite. In short, it gives a sense that Mirrodin Pure would have been all about that. Plus, seeing as the card is legal to play, so in a sense, Mirrodin Pure does exist in a roundabout way.
But that is, in the end, all we got: one card.
One card of what could have been well over a hundred.
It's not that often that gaming companies opt for one way and try to keep it a secret until it comes out, but Magic tried to do that in 2011, even hinting at what could have been.