Amnesia: The Dark Descent

For this one you’ll need to rescue Agrippa at the end. You'll need to create Weyer's Tonic and use that on Agrippa so that you can cut off his head and take it with you. Once you’re at the ending room and Alexander is giving his monologue you’ll need to wait until the portal opens, use Agrippa’s head on the portal, and then you’ll get the achievement. I go over how to make the tonic and get the achievement in the video guide here.