Thirteenth Tribe (RDM)

The Thirteenth Tribe is described by priest Elosha as leaving Kobol and its sister tribes some 2,000 years before the remaining tribes leave to form the Twelve Colonies of Kobol (The Eye of Jupiter).

"...The Sacred Scrolls tell that the 13th tribe left Kobol in the early days. They travelled far and made their home upon a planet called Earth...which circled a distant and unknown star." (Miniseries)

During some period, travel appears to have taken place from Earth to Kobol, as the Sacred Scrolls give an account of the journey to Earth. The effect of Earth on the 12 other tribes is significant, as Laura Roslin states that the star patterns from the Earth Zodiac shown in the 3D projection in the Tomb of Athena were used for the original flags of the Twelve Colonies, and the colonies' original names match the Earth names of the constellations (Home, Part II).

At least a few of the Lords of Kobol remained to watch the 12 tribes leave Kobol. One of them is Athena, who kills herself in grief over the exodus.

The Tomb of Athena was the first marker on a path to Earth (Home, Part II)

Commander William Adama falsely claims to know the location of Earth, using the lie to give the battered remnants of humanity a cause and reason to hope after their escape from the devastated Colonies (Miniseries). Later, through the efforts of President Roslin, Adama and others locate a tomb on Kobol, which reveals a map and sufficient references to point his Fleet to the true general coordinates of the legendary Thirteenth Colony of Earth (Home, Part II).

A beacon near the Lion's Head Nebula, left by the Thirteenth Tribe, but found by the Cylons (Torn)

Over a year later, an ancient probe, possibly the first tangible evidence of the Thirteenth Tribe's existence is recovered by the Cylons in the Lion's Head Nebula. The probe contains a microbial virus that proves particularly virulent to the Cylons on the baseship that recovered it. The Cylons fear the virus so much that they abandon the baseship, moving their Resurrection Ship away to prevent any dying Cylons from resurrecting and transferring the bioelectric component of the pathogen to the Cylon populace. The probe is later destroyed after the baseship self-destructs ("Torn", "A Measure of Salvation").

The Thirteenth Tribe apparently has used one planet as a waystation in their journey. They settled on a planet and built a temple to five priests that worshiped what was apparently a controversial deity. Over 4,000 years later, the Temple of Five is discovered by the Fleet. The refugee Colonials believe that an artifact called the Eye of Jupiter resides there, which is another marker on the path to Earth (The Eye of Jupiter).

The Temple of Five, a curious marker (Rapture)

No such artifact actually exists, however. The Eye of Jupiter is, in fact, the image created by the planet's dying sun. A strange and highly improbable sequence of events occurs when both Cylon and Colonial forces meet at this unremarkable "algae planet" to find the legendary lost temple near the moment of the star's imminent nova. After they leave the system, the Colonials discover that the nova resembles another older nova that occurred in the time of the Thirteenth Tribe's exodus, located in the Ionian system, and believe that they have found a new marker to Earth.

The Temple was apparently designed for a human to witness a vision of some kind as the star begins to nova. Instead of a human using the mechanism, however, a Number Three Cylon uses the device, believing that it would reveal the identities of the final five Cylon models intentionally or accidentally lost to the Cylon history. Only Gaius Baltar witnesses this mechanism in use, but is reluctant to use it himself until it is too late, when the mechanism shuts down as the nova's light is replaced by the shadow of its shockwave (Rapture).