Ares is known as the God of War in Kobolian mythology.
A Cylon simulacrum purporting to be Ares is discovered by a party from Galactica, finding him aboard a genuine Kobolian ship that the Cylons had somehow discovered. After being resurrected, Ares spins a tale about how he left Kobol with the others, which raises Adam's suspicions. During his time with the Colonials, he earns their respect, admiration, and trust through feats of super-human prowess and heroism, such as saving a young boy named Geb from his death—after using some form of external force to damage the structure that Geb is trapped in (The Enemy Within #1—#2).
He earns the attractions of Athena, who he later beds. After bedding her, he leaves and overloads the temporal overdrive, destroying it and damaging Doctor Wilker, who is himself a cybernetic machine sent by Baltar. Ares is able to disable several key systems during the meantime, which Galactica's crew views as natural equipment malfunctions (The Enemy Within #2—#3).
Ares is later found out after recovering data from Wilker's positronic brain, leading Apollo and Starbuck to thwart Ares's other attempts at destroying Galactica. In saving Galactica, Starbuck traps Ares in an escape pod with himself, which is ejected into space before Ares self-destructs, destroying the pod and presumably killing Starbuck (The Enemy Within #3).