No main quest
Nacht der Untoten has no main quest and no Easter egg with steps to follow. What it hides are small things: in World at War a radio and some writing on the walls, to which the Black Ops version adds a song of its own, Undone.
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The secrets of Nacht der Untoten in Black Ops: how to play Undone from the three red barrels outside the starting room, the radio of the Help room and its Dead Ops Arcade music, the writing on the walls, the unfinished Help door and what Black Ops changed.
Nacht der Untoten has no main quest and no Easter egg with steps to follow. What it hides are small things: in World at War a radio and some writing on the walls, to which the Black Ops version adds a song of its own, Undone.
Undone, by Kevin Sherwood, is the musical Easter egg of the Black Ops version: an instrumental rock track of about four minutes, built around an electric guitar solo. It was first written for a campaign mission of Black Ops that was later changed.
Since it needs nothing but a gun, the song can be played on round 1 of a First Room game.
In the Help room, on a table to the right of the Mystery Box, stands a radio. Knife it or shoot it and it plays a song; hitting it again moves on to the next one. In World at War it played tracks such as the Black Cats theme or the Königgrätzer Marsch. In Black Ops it plays music from the campaign and from Dead Ops Arcade. It is behind the Help door, so out of reach in a First Room game.

Chalked on a wall of the bunker. “Ascend from darkness” was also one of Viktor Reznov’s steps out of the Vorkuta prison in the Black Ops campaign, and later a step of the Origins main quest.

The word “Help” painted on the door between the starting room and the Help room was never finished. Without the bottom of its P, it reads “Hell”.
In World at War, both the red barrels and the trucks outside the starting room could be blown up. In Black Ops, only the barrels can, and three of them carry Undone.