Octavius is Julius Caesar's adopted great nephew and heir; he is part of the triumvirate formed after Caesar's death, with Lepidus and Marc Antony as the other two.
It is not until Act IV that Octavius is introduced. At a house in Rome, he speaks with Antony, who is compiling a list of political enemies as the republic is in turmoil. Antony sends Lepidus to "fetch" Caesar's will; while he is gone, Antony remarks,
This is a slight unmeritable man,/Meet to be sent on errands; is it fit,/The threefold world divided, he should stand /One of the three to share it? (IV,i,12-15)
Octavius shows himself to be much nobler than Antony who is treacherous and cruel. Octavius questions this deprecatory view of Lepidus, asking Antony why he thought Lepidus was competent enough to assist in the list of political enemies but now he is only good for running errands. Antony intends to use Lepidus much as Cassius used Brutus to serve his purposes. Unlike Antony, Octavius finds Lepidus "a tried and valiant soldier" (IV,ii,29).
Later, at the battle of Phillippi, Octavius again disagrees with Antony, following his own military strategy, challenging Brutus and Cassius to "come to the field." When the conspirators are defeated and Brutus dies, although Antony acknowledges that Brutus is "the noblest Roman of them all" (V,v,68), it is Octavius who calls in the armies,
According to his [Brutus's] virtue, let us use him/With all respect and rites of burial./Within my tent his bones tonight shall lie,/Most like a soldier ordered honorably./So call the field to rest, and let's away/To part the glories of this happy day. (I,V,76-81)
This commanding presence of Octavius in William Shakespeare's "Julius Caesar" suggests the future stability of the Roman Empire; later Octavius is made Emperor.