Final answer:
The statement is true; Frigg did tell Loki that the mistletoe never swore an oath to protect Balder, leading to Balder's death due to the mistletoe's use by Loki.
Step-by-step explanation:
The statement "Frigg tells Loki that mistletoe never swore an oath to protect Balder" is true. In Norse mythology, all things had promised not to harm Balder except the mistletoe. Loki, the trickster god, found this out from Frigg and fashioned a dart from the mistletoe to exploit the only vulnerability that Balder had.
The mistletoe's absence of an oath allowed Loki to trick Hodr, Balder’s blind brother, into killing Balder with it. This event is one of the most famous stories from Norse myth and signals the beginning of the downfall of the Norse gods, leading up to Ragnarok, the end of the world.