The only character in "In a Dark Time" is undoubtedly the poet himself: Theodore Roethke. Roethke suffered mental breakdowns throughout his life and is now considered to have had bipolar disorder. While he was a writing teacher at university in 1945, he suffered a well publicized breakdown that lead to him seeking help. At the time of writing "In a Dark Time" in 1960, he was seeing a therapist six times a week.

That certainly explains the darkness of the poem and the feeling of despair it expresses in the first stanza.

In a dark time, the eye begins to see,
I meet my shadow in the deepening shade;
I hear my echo in the echoing wood—
A lord of nature weeping to a tree.
I live between the heron and the wren,
Beasts of the hill and serpents of the den.

However, like in other Roethke poems, he doesn't continue bemoaning his life and mental illness, but talks about finding a path that leads him to accept himself and as he states "climb out of my fear."

Keeps buzzing at the sill. Which I is I?

A fallen man, I climb out of my fear.

The mind enters itself, and God the mind,

And one is One, free in the tearing wind.

Partly this could be down to the fact that he had experienced tragedy and feeling of abandonment from an early age. For example, his father died of cancer when he was only 14. As such, his life had always been a journey to rediscover himself and find out what could make him happy. In this poem he suggests it would be to just accept and even embrace the fact that he has a dark mind.