I couldn't get Oblivion Walker to unlock in my first play through, even though I had collected 15 daedric artifacts at various times. So, I assumed that you had to have them all at once. With that in mind, I started a second playthrough. Tonight, standing in my house in Whiterun, I have on my person, all at the same time, the following items: 1. Black Star, 2. Ebony Mail, 3. Mask of C.V., 4. the Oghma Infinium, 5. Saviors Hide, 6. Volendrung, 7. Mehrunes Razor, 8. Ebony Blade, 9. Dawnbreaker, 10. Mace of Molag Bal, 11. Ring of Namira, 12. the Skeleton Key, 13. Spellbreaker, 14. Wabbajack, and 15. Skull of Corruption. BAD NEWS. The achievement still doesn't unlock. The skeleton key is SUPPOSED to count, right? There's one more daedric artifact possible for me (Sanguine Rose), but that Sam G. guy has not appeared at any tavern so far. I would sure appreciate some advice from anyone who knows about glitches with this achievement.