What is the name of the ritual purification ceremony meant to avert evil?

The ritual purification ceremony meant to avert evil is called Lustratio. This ceremony was an important aspect of ancient Roman religious practices, typically involving the purification of people, places, or armies. The term "lustratio" comes from the verb "lustrare," which means to purify or to cleanse, reflecting its purpose of spiritually cleansing and protecting individuals or communities from malevolent influences.

During a lustratio, offerings were often made to the gods, and certain rites were performed, including the sprinkling of water and the recitation of prayers. This ritual would commonly take place in conjunction with other significant events, such as military campaigns or the dedication of a new building, symbolizing the need for divine favor and protection.

While Lemuria refers to a festival held to appease restless spirits of the dead, Compitalia is a festival dedicated to household gods, and Magna Mater pertains to the cult of the Great Mother, these do not specifically represent the act of purification intended to avert evil that Lustratio embodies. The focus of Lustratio establishes it clearly as the correct answer in the context of purification rituals within Roman religious tradition.