The arrival of a new Splinter Twin combo in Standard means its “return” to Modern probably isn’t as exciting. We’ve all seen that song and dance before, right? Still, this Modern build’s ability to interact and set up its hand makes it a deck you shouldn’t sleep on.
The Copycat combo hasn’t put up the best numbers in Standard, but it offers turn-4 kill potential. Saheeli Rai copies Felidar Guardian, the Guardian blinks Saheeli, the Saheeli copies the Guardian, and you repeat that as many times as you want. The issue is how little each card does without the other, so you’ll need to find a way to both maximize that value and make sure the rest of the deck is functional.
Modern Jeskai offers a plethora of creatures you can happily target with either a Saheeli Rai or a Felidar Guardian trigger. Near the top of that list is the prolific Snapcaster Mage. While we have a similar effect in Standard with Torrential Gearhulk, the flexibility and low cost of Snapcaster Mage are huge incentives. You can play a bunch of 1-mana spells, Snapcaster one back on turn 3, and then Saheeli your Snapcaster turn 4 to cast another 1-mana spell.
Wall of Omens is a decent blocker, and draws a card when it comes into play. Turning a Saheeli minus or Guardian blink into an extra card isn’t thrilling, but it’s still value.
Pia and Kiran Nalaar can create an entire army to go on the offensive or to defend a planeswalker. Being able to throw all of these extra tokens with Pia and Kiran’s ability (keep in mind the token Saheeli makes will also be an artifact you can throw) is a nice bonus.
Your suite of 1-mana spells is what makes sure this deck is strong. You have to be able to interact early and effectively, and you need Snapcasters to maximize value. Lightning Bolt and Path to Exile deal with many of the format’s best threats and are the most efficient removal spells you could ask for.
Spell Snare counters many of the format’s important cards to make sure you stay on tempo. Dispel is more limited, but it’s a nice way to interact for just a single mana and will stop many of the format’s important cards that could break up your infinite combo.
Remand isn’t at its highest value here, but it does provide a little tempo and a chance to set up. When your opponents are trying to interfere with an infinite combo, just buying a single turn can be enough.
Spreading Seas can keep your opponent from casting too many spells. This can sometimes completely shut down a deck like Tron or Eldrazi, but even Jund-style decks can struggle to cast 1 or more spells per turn when you shut down a critical dual land.
Saheeli combo isn’t as powerful as Twin since the creature doesn’t come down at instant speed, and tapping a permanent with a 3-mana Deceiver Exarch is typically better than blinking one at sorcery speed with a 4-mana Felidar Guardian. That said, this combo is legal, and it’s powerful, so if your opponents sleep on it, they’re going to get beat by it.