Much like last week's Five-Color Shrine deck, Rin and Seri Cats & Dogs was way better and more powerful than I thought it would be, but I'm not sure it can be truly competitive in Standard because the top couple of decks in the format (Bant Mythics and Temur Reclamation) are so powerful and punishing, while Ugin, the Spirit Dragon is also a blowout if we can't kill our opponent before it hits the battlefield
In essence, you could exile a bunch of instants or sorceries from your hand to tee up a big flurry aimed at your opponent, while also getting access to more card draw with which to punish them
If you have cards that have an Upkeep cost or benefit, those will trigger as well
It hits for 18 damage in a 4-player game on its own, and any sort of on-combat benefits really push it over the top
Disa would really love a Buried Alive, but Graveyard Overdrive has plenty of ways to mill your deck to potentially find a Lhurgoyf to bring into play
Those will fetch a pretty penny, with The Great Henge and Cavern of Souls already hitting over $50