Going to go through my 4 other pokemon and why they benefit this week's core.
Swampert fills two important roles; first it walls thundy and secondly adds wide guard support. Earth Power is nice to take out Jirachi so Metagross can hit Kyurem or Diancie or what ever other guy its redirecting. It does well vs LandoT was well.
Here is a cool serp set. It has a nice move pool and I think a lot of people will start trying other sets with it rather than typical max SpA and dragon pulse, leaf storm, ect. So with tuant and glare I use 252hp rather than 252spa since leaf storm boosts its spa up. Glare is cool to para ground types and being grass it gets around amoonguss rage powder. While being a big threat to Diancie and taunting Jirachi.
Up to here I feel like I have sufficient checks and counters for THALK, Diancie teams, Kyurem, Heatran, Aegi, Rain, Trick room, and most other common threats.
What I am lacking is ground immune, another Talon check, and I am weak to sun aside from stone edge Blaziken.
Cress can do well in the sun with her moonlight and Calm Minds. Getting some calm minds up allows her to become a target while my other guys can go really offensive. She is obviously great to take hit when needed as well. I run Ice Beam to take out other LandoT and a more offensive set with expert belt, but may change to goggles, but haven't felt the need to yet.
Lando my other ground immune checks the talonflames and charizards. I am going with knock off over super power because I dont feel the need for 3 fighting moves and I want a strong dark move to hit trick room setters.