Earth

The Earth was created solely by God.

It's a planet that respectively supports a large variety of life, including bacteria, humans and animals. Entities like angels and demons can manifest on Earth via possession or the use of vessels. Others can appear physically by assuming human form.

The Archangels wanted to wage war on Earth, Michael and Raphael to generate paradise, and Lucifer to purge it of its filth: humans.

According to Chronos, the Earth is soon to be covered in black ooze, i.e. the Leviathans.

Reapers are needed to escort deceased souls to the afterlife, whether it be Heaven, Hell or Purgatory. After deals are up, Hellhounds appear, kill them, and drag them down to Hell.

Known rulers

 * Pagans gods - According to Kali, their religions were practiced before God's was.
 * God - God created mankind, but hasn't had a hand in ruling the Earth for some time, but according to rumor, he's somewhere on Earth.
 * Castiel (temporarily) - After absorbing all of Purgatory's souls, he become the supposed ruler of the Universe.

Inhabitants

 * Humans: The dominant species on the planet. They are often considered the greatest creation of God, and unlike angels and demons, they are neutral in the Heaven-Hell War, not including hunters like the Winchester Family.
 * Animals: There are thousands of billions of species of animals that live on the world. Unfortunately, some of these animals have been driven to extinction by humans.
 * Death - Normally kept restrained down 600 ft under the Earth's crust, but is free due to Lucifer's spell.