Simoun is the alter ego of Juan Crisóstomo Ibarra. He has the appearance of a foreigner, an American, though of diverse ancestry. He dresses like an Englishman and wears blue-tinted glasses, has a short beard, and has long white hair. Simoun is a wealthy jeweler, and is sometimes referred to as Jewish due to stereotyping. He has close ties to the Captain-General, the Spanish governor of the Philippines. The two met during struggles in Cuba where he fought alongside the general and lent him money. Simoun followed him to the Philippines, and uses their friendship (and his wealth) to persuade him to issue decrees and laws that further subjugate the Philippine populace. This is a critical element of Simoun’s plans for revenge.

Simoun’s revenge originates in the first novel, Noli Me Tángere, where he is known as Juan Crisóstomo Ibarra. Ibarra obtained an education in Europe due to having a wealthy family. His father earned the ire and jealousy of Father Dámaso, who had him imprisoned; in prison, he died. Ibarra returned to the Philippines shortly after his father’s death. Ultimately, Ibarra met a similar fate to his father, and his betrothed María Clara entered a convent where she was repeatedly abused by another corrupt friar, Father Salví.