The Otherworld, also known as Faerie, is a demiplane connected towards Megacrossover Earth that is often poetically refered to as "the land beyond the rainbow". It is home to most species of supernatural creatures known to humankind. Its humanoid inhabitants are collectively known as the fae and come in many forms, although most of them are human-sized or smaller. Non-magical humans rarely visit the realm and those that do usually have a significant amount of fae ancestry.
In prehistoric times, passageways between Earth and the Otherworld were more common. Mundane humans were normally barred from travelling to Faerie, although a few exceptions were made. In more recent millenia, the passageways have been closed by the Elder Gods to the point that travel from one realm to another can only be attained by very powerful magic.
On occasion, normal animals from Earth have been traveled to the Otherworld through its passageways and give birth to magical creatures. Crocodiles and lizards would give birth to dragons, horses to unicorns and pegasi, and human women to elves, dwarves, and other humanoid creatures. In many cases, animals will gain sapience and the ability to speak the language of the nearest intelligent being. Many magical creatures have visited Earth, but this has been less common due to Earth's overall magic decline.
The most well-known region is the large island Aman, home to the High Elves, along with some dwarves, hobbits, Ents, and other beings from Earth's distant past. It includes the realms of Asgard, Vanaheim, and Alfheim. Aman was once part of Earth, but it was transported to the Otherworld during the Númenorian Invasion in 23,500 BCE. Normal humans have been barred from visiting Aman, but on occasion, they have been allowed to travel to the smaller nearby island Tol Eressëa.