>>36430236An alien virus that mutated into a Pokemon, it came to the world on a meteor. It changes forms (in gen 3 it depended on the game, later you could manually change it with a meteor item at museums and such). It is usually mythical (i.e. event only and not found without a time-limited pass or gift in the games) but in the 3DS remakes of Gen 3, it was catchable as a regular legendary would be, emerging from a meteor in space that you smash apart before it hits the planet.
Functionally, the forms are focused around a stat spread (speed, defensive, attack), with Attack being a better version of the normal one.
