Very little. The time pokemon is supposedly named Dialga, the space one is named Palkia. The third is called Giratina, but information about it is... virtually impossible to find. All I can locate is scattered references to a "distorted world" or "reverse world", which Giratina either rules or is, somehow. Supposedly it always remains there, and it emerging into this world is a calamity... or is a response to a calamity, again it's not really clear. I'm not even sure the people who wrote down the legends knew.

There are also hints that Giratina rebelled against an even greater Pokemon, some sort of beast with a thousand arms which emerged from an egg out of nothingness, then shaped the world. Sort of a Pokemon creator diety. I only ever found one text that mentioned this creature, and it was old, faded, and nearly impossible to read. I honestly don't even know if I have the description right, and even if I do, it's a creation myth. It's probably not literally accurate. But if that being does exist...