I only know how to unlock the first 4, spoilers below.
Damnatory Knowledge: Keep fighting the imp and submitting to him ("Pleasure him"), then when he asks, "Tell him you want to keep seeing him grow" and then "Accept" his offer. From this point on, he will be named Kanathar. When you enter Apothus's/Nyx's realm, go back and inform Kanathar rather than hide it. If done correctly, Kanathar will arrive the black sun to claim its power.
Memories of Demonic Ascent: Fight Kanathar and win.
Memories of Kanathar: Fight Kanathar and lose.
Word of Power: After completing Memories of Kanathar, recruit him in any way, domination or submission doesn't matter. While having sex, you will have the option of saying his name, getting the achievement.