The Tears of Tjahzi are magic pearls created by the goddess Frigg. She turned them into a talisman of love and friendship. Instead of giving them to Thorgal, she gave them to Aaricia by sliding them into her palms at the moment of her birth. This was an indication that the real gift to Thorgal was Aaricia.
Aaricia used them to cure Vigrid of his blindness by letting the sunlight shine through them, thus creating a rainbow that restored Vigrid's vision.