As a disclaimer this is all my interpretation and I will take fair criticism.
I just want to thank treyarch for trying something new and making zombies and I want to thank maluka, kevin sherwood, elena seigmen and clark s nova for making in my opinion the best music and making zombies a blast.
As you all know the new zombies map Gorod Krovi has two easter egg songs: Dead Ending and Ace Of Spades but for the sake of this post I will talk about the info in Dead Ending.
In the song we can find the verse "My running nightmare is to face myself" therefore we know that it is in the perspective of either nikolai or another character in the origins crew but for the sake of discussion I will say that it is nikolai 2.0's perspective, therefore we can say that the rest of the info is from nikolai.
There is info from the start of the song where the verse "can you hear the panicked wings above" is spoken, this can mean 1 of 2 things either nikolai is seeing visions of his own death or flashback's of the stalingrad war.
The other piece of info comes from the line after that where the verses "destroy and create our story's dead ending" are said and it can mean that the crew is trying to prevent their own death by securing their 1.0 souls and sending those as a sacrifice instead of themselves, this might be the reason why monty mistrusts richtofen.
The verse "my view of heaven looks like someones hell" tells that nikolai can remember the great war between the keepers, apothicons and primis, this can be because of 115 disillusion or because the whole of the zombies storyline is a massive cycle which is supported by the verse "the end will bring me back to you" which might mean that our characters are breaking the cycle by jumping universes therefore breaking the flow of time so the cycle can't continue.
The verse "how long can we go before we know we never mattered" can mean that nikolai knows that the universe can't be fixed by destroying and changing universes.
The verse "I see a mirror or does it see me" might be a foreshadowing of nikolai 1.0's death.
The verse "is this my own end they tell me of" moght mean that nikolai can hear a voice telling him of his own demise.
The verse "where did we go wrong did we know" might mean that the plan was supposed to fail when it started.