Ash Phoenix is the adopted son of Norland von Lunebelg and a former member of the Knights of the Round. He defied his upbringing to fight with Rozé as part of the Nameless Mercenaries, alongside the Black Knights. Due to the Geass placed on him by Sakuya Sumeragi, he viewed Rozé as his "most important person." This became his unconscious drive in battle, though he proves his radical loyalty even after the Geass is lifted.

Ash presents himself as a cold, calculating, and professional solider, not speaking unless necessary. He is deeply skilled at piloting his nightmare, marksmanship, and hand-to-hand combat, turning the tables in any given battle. His focus stays on his mission and pays little mind to much else. This is seen in his fighting style, often dispatching enemies with efficiency, and he has a prone disregard for his own safety.

However, his nature is tenderhearted, and he cares for others selflessly, even if he gains nothing in return. This softer side is revealed with his compassion toward stray animals, sending them to shelters or caring for them in his small RV, never bothered that these animals are less affectionate toward him (then toward Rozé). Ash is also shy around women but becomes infatuated with Sakuya while she is disguise as Raspberry. Only toward her he shows his eager and cheerful self, chatting awkwardly with extreme effort to connect.

Though he is tortured by his past sins, he rises above his own misfortune and grief for the greater good. He stands for justice, not being capable of tolerating any mistreatment of the weak. He chooses honor over his own pride. Throughout his life, he was manipulated and used as a military tool, and yet, this does not stop his resolve to end Norland and keep his word to Juugo Sumeragi. His empathy and fierce desire to protect fortifies his mental strength. His influence and the sacrifices he makes pushes Sakuya to lead the people of Japan with integrity, toward a brighter future.

(Source: Code Geass Wiki, edited)