Teragard

The Human Realm is an otherwise unnamed plane where the humans originate from. At the beginning of the First Age, Guthix found the planet of Gielinor and, after shaping it using Elder Artefacts, he created the Portal of Life, through which he brought a few peaceful races to Gielinor, the humans amongst them. For this purpose, Guthix adapted the form of a human in green clothes. He greeted the humans and created runes for them, and would return to check on them every now and then.

Currently, it is assumed that some humans have remained on their realm, for Guthix only brought a few groups of them to Gielinor. However, it seems that most if not all humans have forgotten about their original realm and think to be native to Gielinor, which they called RuneScape due to the many runes they received. Saradomin, who was a normal human before ascending to godhood, is likely to originate from this realm.

Trivia

 * A human known as King Arthur says to have arrived to Gielinor from a kingdom known as Britain in a separate realm in the early Fifth Age. Whether this means humans live on multiple realms or Britain is, in fact, part of the original human realm remains unknown.