On the initial spoiling of the combo, my reasoning was that it would become a bit too powerful for Standard. Initially, I received some backlash for this opinion, whereas I expect more support. Of course, there would be an eventual realization that Felidar Guardian was ruining the format. As it turned out, those who thought it would be a disaster were completely correct. It was nice to be vindicated. But at the same time, it was a bit depressing that Wizards so clearly overlooked a design blunder.
The Origins of the Saheeli Rai & Felidar Guardian Combo
Saheeli Rai was way too cheap at $5 for the longest time. The planeswalker was already part of a couple of infinite combos in Modern with Liquimetal Coating and Altar of the Brood or Disciple of the Vault. But a competitive list never came out of it. Still, sooner or later, players knew that a card would be released that would make the 3-mana planeswalker part of something broken, right?
REALLY, WIZARDS!? You just brought back Splinter Twin combo... in STANDARD!
Or is it?
Splinter Twin & Deceiver Exarch proved to be such a ridiculously powerful combination in Standard that me and a good many other players left competitive Magic for awhile because of it. Two card combos are absurd when they are as easy to perform on turn four on a consistent basis.
The combo was quite simple. You'd play Deceiver Exarch at the end of an opponent's turn since it had flash. Then the next turn, while an opponent is tapped out, you drop the 4-mana Enchantment Splinter Twin, which allows you to tap a creature to make a copy. Even though the copies come in tapped, the Exarch's ability to tap or untap a permanent can make them untap.
Since the tokens also have haste, you just make enough tokens until your opponent can't stop the damage. Sure, there are ways to disrupt the combo, but it proved consistent enough to spawn its own archetype. The only reason it stopped in Standard was that Rise of the Eldrazi, and thus Splinter Twin, left Standard at rotation in October.
Many players, myself included, refused to play Modern competitively as long as the combo was the heart of a powerful deck archetype there, too. Wizards finally banned Splinter Twin after deciding it was finally time for that combo not to be a deck anymore (Kiki-Jiki, Mirror Breaker still does the same thing as Twin, but it's harder to cast.)
So is the Saheeli Rai & Felidar Guardian combo just as good, or even worse?
Ordinarily, Felidar Guardian is just a good card on its own. But alongside Saheeli Rai, you can create infinite madness. You use Saheeli's -2 ability to make a token of the Felidar Guardian. That token uses its ability to "blink" Saheeli Rai. This means she comes back with full loyalty counters on her. Then you get to use the -2 ability again to continue the process. You rinse and repeat until you have enough Guardians to swing in for lethal damage. Yes, those tokens have haste.
What makes this combo better in some ways is that even if it’s disrupted, either Saheeli Rai or Felidar Guardian can find other targets to make good on their abilities. The Guardian can blink any permanent you control. This means even lands! You can blink a tapped land and tap it again for extra mana! Yes, using the Exarch's flash ability to enter on an opponent's end step can be better. A lot of times you'd tap down an opponent's land to make responding to your combo with counter magic more difficult.
In Modern, you can play Exarch in this deck, too! In fact, you can build a really, really good Jeskai Control deck with these two cards! Saheeli Rai can even Scry 1 for you and deal 1 damage to each opponent! Then you get to play all the counter magic and burn spells your typical Jeskai deck would already play! Saheeli can also copy other creatures and artifacts you control. So you can still get value from either half of the combo even if the other half becomes somehow unavailable.
Fortunately, as good as the interaction between these cards are, it's not going to be as dominant as the combination of Splinter Twin & Deceiver Exarch became. There are instant speed ways to deal with the Guardian, like Fatal Push with Revolt active. There is Declaration in Stone in Standard, and potentially Fatal Push, as well. But the Declaration is still Sorcery speed, so it could still be too late of an answer. It’s also possible to burn away Saheeli before the Guardian can copy her, which is fairly easy to do since she brings herself down to a single loyalty. So it’s a bit easier to disrupt than Deceiver Exarch and its 4 toughness was during its Standard days.
In Modern, you can stop the combo from resolving with Abrupt Decay targeting Saheeli Rai, particularly if you use it in response to the planeswalker’s ability. Even though the -2 ability would take priority, by the time the copy of the Guardian resolves, there will be no Saheeli Rai to blink. Saheeli Rai can be dealt with quite quickly with Lightning Bolt, as well. Path to Exile and Dismember will do the trick, too, just as they always did for dealing with Deceiver Exarch. So this combo is also a bit easier to stop in Modern than Twin was.
Still, this combo was still a strong one to build around in Standard. Many players are shocked that no one at Wizards R&D caught this very obvious combination. Some people called for an emergency ban of Felidar Guardian. One Twitter user also demanded an apology from Wizards for their oversight. It seemed that Wizards committed an extremely obvious design blunder. Aether Revolt was already considered an overpowered set as it is, so creating a new infinite condition seems just absurd.
Is the Saheeli Rai & Felidar Guardian Really Broken?
As good as this combo is on paper, many people thought it was more of a "fixed" Splinter Twin combo if anything. The argument was that there wasn't a lot of card selection spells in Standard right then. This meant that consistent Turn 4 wins are a lot less likely than they were years back. However, while the Saheeli Rai/Felidar Guardian deck wasn't quite as consistent as Splinter Twin combo decks were, it proved to be an effective win condition.
Did one or both cards actually need to be banned? There was the sentiment that it would likely take the printing of other cards to bring this deck to a dangerously over-powered level. However, with Wizards now making banned and restricted list announcements more often, players decided that if it did become too busted, it would be dealt with.
In the early going of Aether Revolt being legal in Standard, Saheeli Rai & Felidar Guardian combo decks performed quite well. Jeskai Saheeli was the most successful build at the outset. A Jeskai Saheeli deck placed 7th at SCG Columbus. There are also four-color Saheeli decks that are performing well, and are also often known at Copy Cat Combo. Even in Modern, Copy Cat Combo has also seen some success, at least on Magic Online.
In paper Magic, the deck quickly won at least one major Standard event. Dylan Donegan of MTG Card Market took down SCG Richmond with his Jeskai Saheeli deck! So while the archetype hadn't broken the format just yet, it quickly became clear that the combo was definitely a good one to build around. As a deck that can win, players battled to find the best version of this deck!
By late April 2017, so many Saheeli Rai & Felidar Guardian combo decks (affectionately known as Copy Cat Combo) had won an unbelievable number of events. It finally became clear to Wizards that the Copy Cat combo had actually become almost just as bad as Splinter Twin had been. It was announced that Felidar Guardian would be emergency banned in Standard as of 4/28/2017, as to not ruin a brand new Standard format featuring the widely praised Amonkhet set.
Was the Copy Cat combo a design blunder on the part of Wizards? Clearly, this particular interaction was overlooked. It was definitely a strong enough combo to be at the core of a Standard deck from the get-go - and perhaps a solid Modern build will still be found in the long run. Fortunately, Wizards recognized that Copy Cat combo was becoming oppressive in the format, before it became the Splinter Twin combo in Standard all over again.
Of course, another deck would take Copy Cat Combo's place in needing the banhammer. But that was for a much different reason, and that's a whole different story altogether.