In the book Last Watch (also published as Final Watch) by Sergei Lukyanenko, the seventh level of the gloom (or Twilight) seemed to contain ghosts or something, but I never truly understood what was going on. What happened in the seventh level of the gloom?
The 7th level is our world that we live in.
The Twilight is cyclical: the colors starts to fade up to 3rd level and then get slowly back to level 6, which is a place, where all the dead Others exist. It is a pale version of the real Earth. Then there is the 7th level... which is the place where you started.
But getting to the 7th level of Twilight is not easy: Merlin in his prophecy said (quoting here from memory) that:
You need to be as strong as me or as smart as me
Getting from level 6th to 7th is almost impossible (it requires a power of zero-level magician like Merlin or Nadya) or you have to get back through levels 5-1 to the real world (but you need to figure it out - > so you are smart as Merlin).
Now as what has happened:
Anton goes to activate the Crown of All Things, which is indeed hidden in the seventh level. Merlin put the spell in the ancient stones of the Edinburgh Castle. The Final Watch appears, but Anton will not be bothered with them. Edgar got things wrong; the thing the Others in the Twilight want most is not resurrection, but death. There is no paradise there, they are stuck forever in a world where everything is just a pale copy, trapped in an imitation of life. They want it to end, because once they fully die, they can be reborn. Merlin has foreseen this and created his spell (its Twilight-destroying effect is temporary). However, the lost Others asked Anton to forgive, so he allows Gennady and Edgar to die, so that they can join their loved ones before it is too late. Arina chooses to live. Then Anton activates the Crown, and all Others in the Twilight die, including the incapitated Dark Others in the Plain of Demons.