In CE, after getting and identifying the Shadow Amulet, Staroxia often doesn't recognize that you have it and she doesn't offer you the quest to become Shadow Lord.
Fortunately, I saved before returning to her after the Shadow Ruins. I never thought much of this bug because it only took 1 or 2 reloads. But this playthrough (29), I had to reload 8 or 9 times, just like earlier versions bug concearning the Unholy Arc issue.