They are planet like aliens born around the same time as the Universe, capable of living for billions of years. For more info on Mugoterrans, go to Terra. They lack the ability to reproduce, being born from cosmic dust and cosmic clouds. They sometimes hide as regular planets, harboring various species.
There's not much to tell except that their species were formed not too long after the universe began, long before other planets.
They sometimes harbour other species on and beneath their surface. Sometimes, these creatures serve as anti-bodies, aiding the planet in defending them even though they can handle it, and in return, the Mugoterran supplies them with good weather and food.
They also evolved the ability to control their climate and vegetation. Their brains are located near their centre, closer to the North Pole side while their hearts are located nearer to the South Pole.[]