Soon afterward, Gunnar, Gudrun's brother, decides to woo Brunhild to be his wife. Sigurd, who has married Gudrun after having been given a potion to forget his previous vows to Brunhild, aids him. Brunhild can only be wed by a man who will ride through the flames around her tower; Gunnar is unable to do this, so Sigurd takes his shape and performs the deed for him. While Brunhild is reluctant to marry Gunnar, Sigurd in his disguise reminds her of her vow to marry the man who can cross the flames. The two then wed and Sigurd places his sword between them for three nights while they share the marriage bed. Sigurd and Gunnar return to their normal shapes and take Brunhild back to Gunnar's hall.