The origin of the star lotus world

Chapter 2438 Main Text
Chapter 2343 of the main text

In the first generation of that game, Mewtwo was already a very high-level Pokémon, along with the legendary birds Zapdos, Moltres, and Articuno. Later, upgraded versions introduced top-tier legendary Pokémon like Lugia and Ho-Oh. At that time, the total number of Pokémon already exceeded three hundred, and the number continued to grow. Then came the ancient Pokémon Groudon, Kyogre, and Rayquaza. Later still, Palkia, Dialga, Giratina, and Arceus, the legendary Pokémon introduced in the Pokémon games, appeared. Later still, there were White Dragon, Black Dragon, and Ice Dragon. White Dragon or Black Dragon could fuse with Ice Dragon to create another Pokémon; for example, White Dragon could fuse to create White Reshiram. Next came Yveltal and Zygarde, and then Solgaleo, Lunala, and others.

The information I've provided about the iconic Pokémon of these generations is incomplete. I haven't looked into the later Pokémon systems much, so I don't know some things.