Legendary Creature — Dog Cat is all you really need to know to get excited about Rin and Seri, Inseparable, but there’s plenty of extra text to dig through after the 4/4 body for four mana.
Whenever you cast a Dog spell, create a 1/1 green cat creature token.
Whenever you cast a Cat spell, create a 1/1 white Dog creature token.
Dogs and cats working together is a beautiful thing and a deck full of both will lead to a massive army of them in no time. But what will you do with a battlefield full of furry friends?
RGW, T: Rin and Seri, Inseparable deals damage to any target equal to the number of Dogs you control. You gain life equal to the number of Cats you control.
The ability is very similar to Zenith Flare from Ikoria, but can be used to nuke something every turn. To fuel the cannon, hounds are being changed to dogs and Ikoria introduced plenty of new cats and kittens to work with the Naya legend. Creatures like Cubwarden, Lurrus of the Dream-Den, Kaheera, the Orphanguard, Frondland Felidar, Bronzehide Lion, and Ajani’s Pridemate all are Standard legal and waiting to team up with Rin and Seri.