Oblivion Walker

Oblivion Walker is an achievement / trophy in The Elder Scrolls V: Skyrim. To obtain it, 15 Daedric artifacts must be collected.

There are 17 Daedric artifacts that can be obtained on one save file in Skyrim, but the Skeleton Key does not count toward this achievement / trophy.

Missable Daedric Artifacts
There are 6 Daedric artifacts that could be accidentally passed up on:
 * Masque of Clavicus Vile from the quest A Daedra's Best Friend. It is only obtained if Barbas is spared.
 * Mehrunes' Razor from the quest Pieces of the Past. It is only obtained if Silus Vesuius is killed.
 * Skull of Corruption from the quest Waking Nightmare. It is only obtained if Erandur is killed.
 * Ring of Namira from the quest The Taste of Death. It is only obtained if Eola is cooperated with.
 * Volendrung from the quest The Cursed Tribe. It is only obtained if the Dragonborn does not attack any of the Orcs in Largashbur (unless out of self-defense).
 * Mace of Molag Bal from the quest House of Horrors. It can only be obtained if the Dragonborn obeys Molag Bal and lets Logrolf the Willful go to Markarth, and get trapped by Molag Bal, instead of straight out killing him.

Exploits

If one (and only one) of the Daedric artifacts are irrevokably missed, it may still be possible to get the Oblivion Walker achievement / trophy by obtaining both the Ring of Hircine and the Savior's Hide in the quest Ill Met By Moonlight. There are reports that the 3.01 patch fixed this exploit, but it has been confirmed that they are both still obtainable even after the patch (03/23/12, PS3). The Masque of Clavicus Vile, as well as any other type of apparel, can be duplicated using the mannequin duplication exploit. However, these do not count towards the oblivion walker achievement due to the achievement requiring 15 different daedric artifacts. (Confirmed PC, PS3, and 360) 