This is a Cat Tribal deck that has gone through a couple of transformations since the release of Amonkhet. Regal Caracal is still a crucial piece, but the deck has moved away from the mass production of tokens and toward a more dedicated tribal theme.
Update 1/11/18: Rivals of Ixalan brought us a new GW Planeswalker! Though Huatli, Radiant Champion isn't explosively powerful, the card advantage that she can provide (not to mention her relevant minus ability) might prove to be the key to consolidating some of the card draw elements of previous builds into a less mana intensive package.
Edit 2/27/18: Rivals of Ixalan Standard has been a trip, and actually playing this deck out has yielded several insights. The first is that Blossoming Defense and Shapers' Sanctuary are still very playable cards. The second is that Oketra the True only really dies to Vraska's Contempt and Hour of Glory and supports the go wide plan this deck has going for it.
Testing has showed that in the right match up, Huatli, Radiant Champion is bonkers. In the wrong match up, she's easily boarded out for better support cards and answers, but on anything but an empty board, she does work. The aggressive meta has turned Baffling End into essential early game interaction and Radiant Destiny provides a mid-game anthem effect that can be crucial at keeping creatures out of range of Sweltering Suns and Yahenni's Expertise.
Cats went 3-0 at the Standard Showdown on 2/24/18 but I need to test it in more store metas before I can declare anything about its viability. However, I'm confident that its passive life gain, its enchantment heavy (and thus hard to disrupt) gameplan and its synergistic creature base gives it a lot of ways to compete in this format.
Edit 3/6/18: it's PPTQ Time! Cats has performed well enough each time I've played with it that I think it's well positioned enough to compete at the PPTQ level. Part of what gives me this confidence is my renewed understanding of what this deck's sideboard is supposed to do. If I'm already good against Mono Red, Authority of the Consuls becomes a win more kind of card. I might learn that I am mistaken and I need the extra life gain and haste-hosing, but I think Shapers' Sanctuary and Ixalan's Binding are more important cards to bring in in that match up.
The matchups I anticipate will be difficult for me are Grixis midrange and other midrange decks that lean on cards like Rekindling Pheonix and Glorybringer. The best thing I can do to combat these decks is to accelerate my damage output so as to put them on the back foot prior to turn 4 or 5 with cards like Appeal // Authority, which also help me break through board stalls and push through for crucial points of damage.
Edit 4/12/18:
Rivals of Ixalan Standard is at its close, and Cats have had a great format in the sun. At last weekend's Store Championship, I piloted this build of Cat Tribal to my first top 8 finish in a tournament of that size. It was six rounds of Swiss and I squeezed into the top 8 with a 5-1-1 record. I may have lost to Grixis control but the experience of the day's competition assured me that this deck has major legs and a lot of ways to fight the good green/white fight.
Song of Freyalise and Shalai, Voice of Plenty look to be two new tools for Cats going forward, and I'm excited to find ways to get to Caracal mana a turn sooner than usual, while also having the ability to get under opponent wraths. Sweltering Suns and Hour of Devastation might still be scary, but I'll just have to play smarter in those matchups. Looking forward to Dominaria Standard!
Edit 5/20/18:
Dominaria Standard is in full swing and after puttering around with an abzan build of Constrictor, I'm back to digging into Cats. Seal Away looks to be just the kind of early game interaction this deck was looking for, but otherwise the main deck doesn't need a whole lot of change.
I'm a little cooler on Song of Freyalise than I was during spoiler season but Shalai, Voice of Plenty is definitely a good fit for Cats, even if she doesn't quite make it into the main deck. Burn centric decks are floating around as are hyper aggressive decks. Even if it just buys me a turn to find a drop Caracal, protecting my board and my face from targeted removal is super important. Having a high toughness flier on my side aint bad either.
I never got to try Cats out at a PPTQ last format so 5/26 might finally be my chance!
