Because Athena is the goddess of wisdom and an owl usually represents wisdom.
Athena lived in the past but some say that her spirit still exists in Athens.
living as a spirit goddess in olympus
Leo attacked the Roman camp in "The Mark of Athena" because he was being controlled by the ventus, a storm spirit, that was trying to manipulate him into releasing it. Leo was not in control of his own actions during the attack.
The Greek spirit of victory is Nike. In Greek mythology, Nike is most often associated with athleticism, speed, and triumph. She is often depicted with wings, symbolizing her role as the goddess of victory.
Artemis/Athena?
In the epic poem "The Odyssey," Odysseus goes into town accompanied by his loyal son Telemachus, his faithful swineherd Eumaeus, and the goddess Athena in disguise.
Athena refuses to fight directly, instead relying on Odysseus' warrior spirit to carry the day. She chastises Odysseus when he asks for her help (when she is disguised as Mentor). Athena guides Odysseus' men's spears into their targets, and helps the suitors mostly miss their spear throws.
Athena, the goddess of wisdom, courage, inspiration, civilization, warfare, strength, strategy, female arts, crafts, justice and skill is often accompanied by a Little Owl (Athene noctua). This little guy was so popular he made it onto the Athenian currency, the silver tetradrachm, in 2 BC. Alas, I have not heard of Athena having a Leopard companion.
One only says accompanied by."accompanied with things" & "accompanied by people"
Nike's most common symbol was the palm branch. She was also frequently pictured with Athena and sometimes the goddesses were called Nikai, so Athena's symbols such as the owl and the olive tree sometimes translated to Nike.
Athena was known as the goddess of wisdom, courage, inspiration, civilization, law and justice, strategic warfare, mathematics, strength, strategy, the arts, crafts, and skill. She was often portrayed as wise, strategic, just, and protective of her city Athens. Athena was also known for her fierce determination and competitive spirit in battles and challenges.