The speaker rejects the old comfort that time heals. The opening line is blunt: "Time heals nothing." There's no softening it, and the short, flat sentence feels like a door closing on any hope of getting over something.
From there, memory is called "the bastard child of unrelenting nightmare." That's a harsh image. Memory isn't a gentle record of the past here but something born out of constant torment, unwanted and unable to be disowned. The poem then pictures memories as a "team of ghosts" that have been freed. The word "liberation" is odd and unsettling, since the thing being set loose is the haunting itself. Once "unchained," the ghosts come back "on a moonless night," when it's darkest and there's no light to guard against them.
The mood is bleak, tense and quietly frightening. The speaker sounds worn down, someone who has stopped expecting relief. The poem doesn't say what the nightmare is, which makes it feel both personal and open to anyone carrying something painful.