Bill why is it that pokémon such as Rotom and Spiritomb are not considered legendary pokémon but the Cosmog line are? I used to think that a pre-requisite for legendary pokémon was not evolving, but you can’t say that there can be only one because two different Cosmogs have been identified. Is there even an official way of figuring it out?

Actual rarity and power levels, anonymous. While it’s true that it’s incredibly difficult to find spiritomb and rotom in the wild, neither are so rare that they’re considered mythical or actual cryptids. In fact, spiritomb alone is actually quite common, assuming you can find a an odd keystone (which is uncomfortably common in the highly spiritual Sinnoh).

Likewise, neither pokémon possess abilities on the same level as true legends or even mythical pokémon. While, yes, cosmog and cosmoem technically possess power levels much less potent than rotom or spiritomb on the battlefield, both members of that line possess unique, reality-warping abilities off the battlefield—abilities that rotom and spiritomb and other particularly rare species can only dream of possessing. And then, of course, there’s the fact that cosmog’s final evolutions possess power levels that are far more potent than that of most other pokémon species, so that, in combination with cosmog’s natural abilities, simply sets it apart from other pokémon.

In short, it’s not so much rarity alone, anonymous, but rather rarity and what a pokémon can do that form the litmus test of what is and isn’t a legendary.