I decided to use a Mega that OHKO's two of the most popular mons, Diancie and Hariyama. Using 308 Speed to outspeed Roserade and 375 attack to barely guarantee an OHKO on Mega Abomasnow, the rest (of EVs) were invested towards HP. Yet, I put Diancie just in case that speed is not in its favor, TR or not. Of course, Hariyama is there to support TR. Next up, I put the duo of Manaphy and Victini, both with mediocre speed and as baits for Water types. Lastly, I chose Mence since it's a check to physical attackers and a ground immune.
My personal and general checklist (or just things that I had in mind as I built this team):
- 1 Zard X check and 1 resist/immune
- 1 Fire (Camel) check and 1 resist/immune
- 1 Water (Blast) check and 1 resist/immune
- 1 Sleep immunity
- 1 Ground immunity
- 1 Explosion resist/immune
- 1 check and 1 resist/immune for each (because they're common):
- Diancie, Genesect, & Hariyama
- Others: Speed Control
More the merrier.