Dark Messiah of Might and Magic Elements

~THIS IS STORYLINE RELATED~
While you are hunting down Arantir in chapter 8, you will have the option to rescue Leanna. Choose to save her and follow the signs to the Spiders Lair.There will be many small spiders and one very big spider (The Necromancer's call it the Sacred Spider.)The big spider can take a bit, I was a Archer using a bow at first to weaken it then getting in with my Lightning Dagger's when it's health was about half way down. Then run forward and go up the incline and Leanna will be in the corner, untangle her and get the hell outta there, after you get off the elevator this achievement should ding.
~Saving Leanna gives the story option of redemption later on.~

------This mission can be missed and is optional.--------

In Chapter 8, after you have gone through the Library, Lab, Library door to the Pit, and cleared out the Prayer room, you will come to an elevator that takes you down. You'll get off the elevator and travel down a corridor until you come to an open circular room and hear Leanna's cry for help. Xana will suggest leaving her. As you enter the circular room turn left, and then take the first left you can. You can verify that you're on the correct path by reading the little signs. After a ways you should find another elevator that takes you down. This should get you to the Spider Lair.

Even if you went through the portal in Arantir's chamber, and the optional rescue was removed, you can still go back to the Lair and rescue her and get the achievement.