From Sonic Retro
|Species: Cosmo's species|
|Series: Sonic X|
|First seen: "A Cosmic Call"|
Dark Oak is a fictional villain from the Sonic X cartoon series. He is the leader of the Metarex, an army of bio-robots that scours the galaxy for the Planet Eggs, jewels that contain the life energies of the planets. Dark Oak has one large green eye and carries a golden sword.
Dark Oak first appears to challenge Super Sonic in orbit around the alternate Earth. Despite Super Sonic's seeming invincibility in his previous battles, he is unable to defeat Dark Oak. In order to prevent Oak from stealing the Chaos Emeralds, Sonic uses Chaos Control to send them away. As Sonic falls toward the planet, Oak departs for space, revealing damage that Sonic had not noticed. His final act in that incident was to alert his forces to search for the Chaos Emeralds and to send a Metarex to remove Earth's Planet Egg.
Before taking the name Dark Oak, he was known as Lucas and used to have a strong relationship with Hertia, who is Cosmo's mother. He is also of the same race as Hertia and Cosmo. At the time, their planet was constantly being attacked by invaders. The males of the species were forced to transform into large dinosaur-like creatures in order to battle. However, they could not retain this form, and taking it would usually result in death. Lucas had figured out a way to use the planet's Egg to help increase their power and had high hopes that it would save the planet. However, Hertia disliked this idea because it killed the plant life. She decided to gather the females of the species and left Lucas and the others for dead.
During the final battle with Sonic, Dark Oak merges his body with Black Narcissus and Pale Bay Leaf in order to become a three headed dragon. They are only stopped when Cosmo transforms and immobilizes them. Tails then shoots him and Cosmo with the Sonic Driver, destroying them all.
At the end of the final episode, Lucas is seen with Hertia as he takes her hand and vanishes.