Monster Galaxy is a Facebook RPG game based on battling, taming and collecting monsters, like Pokemon. It was produced by Gaia Online and first published online in late 2010.
Monster Galaxy was rapidly developed with a small, dedicated team of artists, engineers and management, the game evolving rapidly over the first six months of development. As this IGN article discussed at the time, Monster Galaxy was one of the few Facebook games at the time that "didn't suck".
You can play Monster Galaxy on Facebook, today.