The Star of David
Once a very positive symbol of Jewish identity, the Star of David came to symbolize the racism and subjugation that Jewish people had to endure at the hands of the Nazis. Although Felix was never forced to wear the Star of David (the Catholic church shielded him), his friends and family had to wear the Star of David. Much like the scarlet letter, the Star of David is a symbol meant to induce shame in the wearer and make the wearer feel that they are less than others around them.
The Swastika
The Swastika is one of the most potent symbols of racism worldwide. Each member of the Nazi party, omnipresent in the world of Once, was forced to wear a Swastika armband when on duty. The Swastika, which was co-opted from Buddhism, is the symbol of the Nazi party, which perpetrated one of the worst genocides and systematic racial violence in history. The Swastika remains a symbol of the far right, Nazism, and racism to this day, reflecting how terrible Nazi Germany was.
The Catholic Church
For Felix, the Catholic Church is a symbol of safety. Few Jewish children who came of age in Nazi-controlled areas remained alive after the Holocaust. Because of the Catholic Church, which took Felix in and sheltered him from racist violence for over three years, Felix survived the Holocaust. The Catholic Church was a positive force in Felix's life and many people's lives.
Death
Death is an unfortunate, but important, motif in Once. Once is set against the backdrop of the Holocaust, one of the most significant genocides in history, and World War II, one of the deadliest wars ever. Felix is a constant witness to death (including to other children, like Zelda), which scars him and shapes his worldview.
