My Gen 6 RNG campaign is underway. In no particular order, these are the legends I've encountered first - Looking for ball and nature recommendations:
Some nature suggestions :
Zekrom - Adamant the primary one , Naughty if you want to use draco meteor/volt switch and to a smaller degree Jolly but in general Zekrom goes for bulk rather than speed since it has not that good of Spe to begin with.
Terrakion - Jolly most of the time since it has a key speed stat out-speeding base 100s , Garchomp etc. Adamant might be used for higher power but usually not advised.
Cobalion - Jolly for Cobalion too pretty much the same reason as Terrakion. To a lesser degree Impish for a defensive set or Timid for a surprising one.
Virizion - Jolly again here , not much to be said about other natures.
Azelf - Due to being fast and having good attack/special attack, it can go for Naive , Jolly or Timid. Jolly is usually used since Azelf has access to explosion/stealth rock making it a great suicide lead. Not familiar with the other two lake guardians.
Thundurus - Timid most of the time for both the normal and therian forms. Normal form might use to lesser extent a naive nature for a mixed set(with superpower and all). Modest is also another option for the Therian form if you dont care about outspeeding both Zards, Jirachi etc.
Heatran - Timid/Calm/Modest, all three are viable with Heatran depending on what your scope is with it.