In Magic 2014, the big twentieth-anniversary-of-Magic twist was that the returning mechanic was one of Magic's most famous - or infamous - creature types, Slivers. The insectoid-serpentine-angular-uncategorizable hive-mind creatures debuted in Tempest block, where only three things were known about them - they were dangerous; they could survive anywhere; and they were most definitely not native to Rath.
They failed to make a repeat appearance even two blocks later in Nemesis, which was set on Rath; and when the plane was overlaid onto Dominaria in Planeshift, they were also conspicuously absent. In fact, it took Slivers until the second set in the Onslaught block, Legions, to be printed for a second time.
Their three-peat came, naturally, in Time Spiral block, and then after Dominaria's storyline was thought to be closed for good, that was assumed to be the last of them. But then Magic 2014 rolled around, and Slivers were given a slight mechanical redesign - their abilities now only affected the Slivers their controllers controlled - and a striking visual one, now resembling Predators more so than Aliens.
Die-hard Sliver fans were unimpressed with both, saying the new art made them look like generic monsters and "not Slivers," and that it was flavorfully important that every Sliver affected every other one on the board.
Still, despite the bad fan feedback, Magic 2014 is proof that Slivers can show up anywhere. Indeed, we still have no idea what their home plane is. So could they ever come back - and if so, when? Let's break it down:
- Core set mechanics are no guarantee that R&D wants to reuse those keywords again after the core set they appear in. They just happen to be simple keywords that are right for the environment. Still, Slivers are an odd thing to introduce new players to without a broader context. After all, Mark Rosewater admitted that they were almost changed to another, entirely new, creature type, which was code named "heroes" - wouldn't something like that have been simpler and more resonant?
- Slivers appear to be one of those things that happens in cycles, like multicolor blocks and cicadas - it took roughly five years between Tempest and Legions for them to show up for the second time, and then about another five years between Legions and Time Spiral, followed by seven years between Time Spiral and Magic 2014.
- The "neo-Slivers" tested very, very poorly. A return to the old art style would be in the cards, but the all-upside mechanic is probably there to stay.
The verdict: We'll see Slivers in the Fall 2016 large expansion or later.