Core Set 2021 For Commander First Looks: Rin And Seri, Inseparable

It’s raining cats and dogs! Sheldon Menery builds his first Core Set 2021 Commander deck around Buy-a-Box promo Rin and Seri, Inseparable!

Rin and Seri, Inseparable, illustrated by Leesha Hannigan

The first Core Set 2021 previews and live and already exciting!  We’ve already seen that Teferi, Master of Time is going to be the face card of the set, but for all us animal lovers, the face card is going to be far furrier.  I bring you Rin and Seri, Inseparable, finally and definitively answering the question.  It was us.  We let the Dogs out

Dogs are all the rage in Magic right now, with Pako, Arcane Retriever being everyone’s favorite good boy.  Rin and Seri ups the ante by adding Cats to the mix in spectacular fashion.  Cats are a better tribe at the moment than Dogs, but we haven’t seen any doggos yet previewed in Core Set 2021 besides Pack Leader.

The first thing to talk about regarding Rin and Seri is the art.  Majestic, beautiful, and heartwarming, it seems like just salve we need for the wounds of these turbulent times.  The foil full art version will certainly be a chase card among the collectors, and you can count me as one of them. 

The dog is out of the sack regarding the creature type.  It’s now been officially confirmed (by Mark Rosewater via Blogatog) that all creatures of the type Hound are now Dog. 


Boiling down what the card actually does, there are three separate elements:  its combat numbers, the triggered ability, and the activated ability. 

As far as combat goes, it’s mediocre, a 4/4 for four mana, three of it colored.  It’s cheap enough that if you want to Voltron it up you can; any buff of three to the power makes it a three-hit killer.  Its activated ability taps it, so you’ll need something to give it vigilance if you want to both battle and activate.  While Rin and Seri are probably going to get into their fair share of combats, the other two abilities are what make it shine.

Whenever you cast a Dog you get a 1/1 green Cat token creature, and whenever you cast a Cat, you get a 1/1 white Dog.  This will lead you down a tribal path, irrespective of the activated ability. Making more things for doing what you’re doing already — namely, casting creatures — is full of value. What you do with those creatures is left up to your discretion.  Certainly, cards like Coat of Arms will make your army of small- to medium-sized creatures well larger. Putting free creatures onto the battlefield will increase the number of triggers you get with cards like Soul Warden or Mentor of the MeekLeyline of the Meek and Muraganda Petroglyphs provide excellent Anthems for your tokens. 

Leyline of the Meek Muraganda Petroglyphs

When you cast a spell that’s both a Cat and a Dog, you get two triggers.  There aren’t any creatures that are natively a Cat Dog save for Rin and Seri, but there are plenty which have changeling and are therefore every creature type.  Mirror Entity is the star of this particular show, giving you the ability to turn up the heat on your opponents by setting the base power and toughness of your creatures to lethal levels. I’m personally a fan of Chameleon Colossus.  Folks tend to underestimate the power of protection from black combined with the ability to double its power.  Add Xenagos, God of Revels for a truly frightening experience for someone’s life total. 

The key ability of Rin and Seri is the activated one.  For RGW and a tap, you deal damage to any target equal to the number of Dogs you have and gain one life for each Cat.  As mentioned, Cats are better than Dogs right now, so you’ll likely be gaining more life, but you know that you can at least do one damage, because of Rin (I’m assuming Rin is the dog, after the famous international black-and-white movie hero, Rin Tin Tin).  With those Shapeshifters, you’ll be able to do more — and who knows what kind of friends that the rest of Core Set 2021 will bring?

There are three abilities that come to mind for adding to Rin and Seri: the aforementioned vigilance, lifelink, and deathtouch. Lifelink and deathtouch will offer you benefits both in combat and for the activated ability.  Deathtouch in particular strengthens the activated ability, since you can now destroy any creature. Lifelink becomes a nice bonus, but isn’t the major point until you’re doing much larger amounts of damage. 

Deck Directions

While Rin and Seri insist that you build a Cat and/or Dog tribal, there are any number of directions you can take a deck. You can go as wide, high, or focused as you want. While not natively given to a Voltron strategy, Rin and Seri are in the right colors to do so. You have access to cards like Stoneforge Mystic and Stonehewer Giant from white and Godo, Bandit Warlord in red to go fetch the Equipment you want. From there, it’s dealer’s choice.

Stoneforge Mystic Stonehewer Giant Godo, Bandit Warlord

There’s a long history of Cats and Equipment in Magic, going all the way back to original Mirrodin, with cards like Leonin Abunas and Taj-Nar Swordsmith.  The Commander 2017 deck, led by Arahbo, Roar of the World, had a major Cats and Equipment theme. Kemba, Kha Regent will make piles of token creatures if it’s Voltron’ed up. 

Because you’re creating token creatures when you cast your tribal pieces, going all the way around is viable.  A nice Overrun, Overwhelming Stampede, or Craterhoof Behemoth will end a game pretty quickly when you have a host of creatures. Cathars’ Crusade and Beastmaster Ascension (after some attacking) will make them extremely large.  You could also likely sneak in a Triumph of the Hordes if your friends won’t get irked by the poison damage. 

Because you’re creating free tokens when you cast spells, there are infinite combos to be had.  There aren’t too many super-easy ones, although Aluren plus Whitemane Lion (or Fleetfoot Panther) works pretty easily and cheaply.  You can add Cloudstone Curio for further hilarity.  Once you have an arbitrarily large number of tokens, you have choices in free sacrifice outlets.  Goblin Bombardment can sacrifice them to deal damage, as can Blasting Station, although you have to go through individual iterations.  Altar of Dementia can mill people out or Phyrexian Altar can create the mana to do some other obscene thing, like a giant Comet Storm

Rin and Seri, Inseparable
Sheldon Menery
Test deck on 06-05-2020

This deck leverages a number of the themes mentioned above without becoming too much a servant to any of them, preserving its playability on multiple angles. I’d really want to do some attacking with Rin and Seri, so cards like Ajani Greathearted and Heliod, God of the Sun give vigilance to the creature suite.  In a multiplayer environment, vigilance is good in its own right.  Giving our commander the opportunity to both attack and use its activated ability steps things up a notch. 

The first card that actually occurred to me for the deck was Basilisk Collar.  It’s another card that’s simply good with nearly any creature you have, but really shines when it comes to Rin and Seri.  Destroy any other creature, gain some life.  With the aforementioned vigilance, you can double dip.

Cat and Dog tribal are present, although the Cat element is much stronger.  There are plenty of changelings to get double triggers.  One of my favorites is Changeling Titan.  It’s a 7/7 for five, and you champion another creature —which means that on-curve you can replace a small creature like Savannah Lions with a bigger beater. It also helps you recover after a sweeper by bringing the original creature back. 

Changeling Titan Disrupt Decorum

Another favorite new card is Disrupt Decorum, which opens the path for our creatures to attack by goading everyone else’s.  There will certainly be unfavorable combat situations, which is only good for us, since we’re not involved. 

We can also get some commander damage action via any of the equipment and either Arahbo, Roar of the World and/or Xenagos, God of RevelsBatterskull will get us there as well. 

The deck shows just a little glimpse of the types of directions you might take what is sure to be a frequently desired and much-beloved creature.  I look forward to the rest of preview season to see what new Cats and Dogs might live together beneath Rin and Seri’s umbrella, as well as looking forward to what kinds of brews you all come up with for our new favorite legendary pair.

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