The Elder Gods are the first true gods of the universe. The Elder Gods were responsible for creating the universe itself, using their immense powers. They used the Elder Artefacts, which were also created by them, to better shape their creations and Gielinor was their perfect and last one.
When Guthix discovered Gielinor, the perfect creation of the elder gods, he was overwhelmed by its beauty, and opened a gateway to bring through peaceful beings to share Gielinor with, "shaping" the plane in the process. Powerful elder god artefacts were lying across the planet when Guthix arrived; the elder horn, the Stone of Jas and the Elder staff, which is known as the Staff of Armadyl. It was those items, along with the elder sword, who granted him the immense power he was known to have. He then decided that the mortals had to fully enjoy the world without the presence of gods so he decided to go into an eternal sleep and before doing so, hide the elder artefacts he had. Seren, a goddess that had very nice relations with Guthix and was present at the First Age as well, promised that she would also enter a slumber with the same objective, but for unknown reasons she did not. Shortly after Guthix entered his slumber, other gods arrived to Gielinor and started conquering it for their cause, which eventually led to the God Wars. This had catastrophic consequences, such as the extinction of many races, the irreversible destruction that Zamorak alone caused to Forinthry, which generated the Wilderness, the desecration of many souls, deaths and pain. After the immense destruction that Zamorak had caused to Forinthry, the Anima Mundi cried with pain, and Guthix woke. He banished the major gods from Gielinor and prevented them from ever returning by establishing his Edicts. Gielinor would not see any more major gods until the Sixth age, when Sliske killed Guthix with the Staff of Armadyl and ended the edicts of Guthix in the process.
|“||Other gods? I've not heard those names before. Guthix appeared frequently to us back in those days. I suppose he wanted to ensure balance and that he wasn't introducing something to this world to upset that balance. He said very little. I think he just wanted us to be aware that he existed and to give us some understanding in those first days. He spoke a lot about balance and encouraging us to live in harmony with our surroundings--to feel free to use our environment, but not to abuse it. It seems that he had not created this world, and spoke of 'elder gods' that existed in a time before he could remember; of this he said little.||”|
Little is known of the Elder Gods, whether it is about their nature or their actions. The only physical remains of their time period may be the Elder Artefacts such as the Stone of Jas (also known as: The Eye of Saradomin or The Fist of Guthix), an ancient artefact said to be used by the gods to create both Gielinorian magic and the Anima Mundi. It was also responsible for creating rune essence. Its location is revealed during the quest While Guthix Sleeps but during the end of The Ritual of the Mahjarrat the stone is hidden at a random unknown location by the player.
It is possible that the knowledge of the Elder Gods has survived up to the current age of Gielinor in the form of the myth of the Elder Dragons discussed in the Book of Folklore. They believe it to have been created to throw doubt on the idea of Gielinor being barren before the gods arrived (the same time period in which the Elder Gods also apparently resided).
The Elder Gods were theorised to be the "masters" spoken of by TokHaar-Hok that created the TokHaar using the Elder Kiln to create and shape the mountains of the world. This is later confirmed if you talk to him after completing The Brink of Extinction. When you ask TokHaar-Hok if his masters are Gods, he states that they are not Gods as the player thinks of them, but far more powerful. The player's Gods are corporeal beings who abused his masters' artefacts to gain power, and in his opinion don't deserve worship. When asked how his masters made the world, TokHaar-Hok states they made powerful tools of creation, and says the player might have heard of one of the artifacts made by his masters, the Stone of Jas. This proves his masters are the elder gods. This possibility was supported by the fact that this happened before the world was known as Gielinor, a name that was only given to the land when Guthix arrived. According to TokHaar-Hok, the TokHaar await the return of their masters to Gielinor, suggesting that they are still alive in the universe. Then again, this could just be Hok's interpretation.
In addition there is also hidden lore about the Elder Gods from the point of view of the TzHaar. This lore is found in a bookcase next to the Fight Cauldron.