Here is the full list of all 24 The Impregnation of the Elves: Conquest of the Arrogant Fairies by Impregnation achievements.
Defeat all the Elves in Challenge Mode
Unlock all achievements
Achieved Ending 1
Victory over Idun
Destroy Idun's armour completely
Achieved Ending 2
Defeated by Idun
Victory over Frigga
Destroy Frigga's armour completely
Defeated by Frigga
Victory over Nimue
Destroy Nimue's armour completely
Defeated by Nimue
Victory over Vivian
Destroy Vivian's armour completely
Defeated by Nineve
Defeated by Dryad
Defeated by Vivian
Victory over Nineve
Destroy Nineve's armour completely
Victory over Dryad
Destroy Dryad's armour completely
Passed a question once
See the Goddess' True Form