Sif was born a second generation goddess of Asgard and eventually became Thor's lover. Sif possesses the conventional attributes of an Asgardian woman ("goddess"). Like all Asgardians, she is extremely long-lived (although not immortal like the Olympians), superhumanly strong (the average Asgardian female can lift about 25 tons; Sif can lift 30 tons) immune to all diseases, and resistant to conventional injury (Asgardian flesh and bone is about 3 times as dense as similar human tissue, contributing to all Asgardians' superhuman strength and weight). Sif's Asgardian metabolism gives her far greater than human endurance during all physical activities. Sif has extensive training in unarmed combat as well as swordsmanship. Her natural fighting ability is only surpassed among Asgardian women by Brunnhilda the Valkyrie.