In Disney’s Frozen II, the mysterious magical caller is identified as the voice known as The Voice.
The Voice repeatedly sings to Elsa from beyond Arendelle, awakening elemental magic and drawing her toward the Enchanted Forest. Elsa hears the call during the film’s opening supernatural disturbance and eventually follows it with Anna, Kristoff, Olaf, and Sven.
The identity of The Voice becomes one of the sequel’s central mysteries. The call is connected to Ahtohallan, the magical river of memory, and to the history of Elsa’s family and the Northuldra. Near the end of the film, Elsa discovers that the voice belongs to her mother, Iduna, heard through a memory from the past.
The voice is performed by Evan Rachel Wood, who also voices Iduna in Frozen II. It is not the same thing as the elemental spirits encountered during the journey, such as the water spirit Nokk, the wind spirit Gale, or the fire spirit Bruni.