Carillon

Carillon, before its destruction

Carillon is the dimly lit home planet of the Ovions.

Relevance

Carillon has rich tylium deposits, which the Ovions had hoped to trade to the Cylons in exchange for independence. An earlier expedition overseen by Baltar noted that Carillon had nothing of note, although these reports were later proven false by Commander Adama.

A resort on the surface of the planet is used by the inhabitants as a lure to kidnap people for the purpose of consuming them (Saga of a Star World).

After the destruction of the Colonies Carillon becomes (despite of its barren nature) the first vanishing point for the view human survivors and the battlestar Galactica.

End of Carillon

Very soon after Starbuck and Apollo set fire to the tylium mines, the tylium ends up leading to the destruction of the whole planet of Carillon. The explosion of the planet also destroys a Cylon basestar along with the Imperious Leader that is aboard (Saga of a Star World).

Notes

• It is possible but not certain that Carillon is the Ovion homeworld: How could the Ovions have survived without food supply from the outside (all through their evolution)? If the Ovions had only the planet of Carillon as world why weren't they called 'Carillons'? (It would also have been a pretty violent human action to wipe out the entire Ovion race!)
• According to Encyclopedia Galactica (a non-canonical piece of merchandise published in 1979):

The tylium-rich Carillon was first discovered by Colonials 178 yahren before the Battle of Cimtar, later settled by a human mining colony 58 yahren later. Since the soil is incapable of supporting crops, the settlers are dependent on supplies from outside sources. Despite this, the colony grew to 50,000 people 15 years after settlement.

Due to the intensification of the Thousand-Yahren War, supply lines became impossible to obtain and the colony was later abandoned, making way for the non-native Ovions to settle, mining the tylium for the Cylons.