What are the characteristics of speaker, the narrator, and Porphyria in "Porphyria's Lover"?

I think you have become slightly confused between the two
main characters of this excellent poem. Your question implies that there are three
characters, but do not forget that the speaker and the narrator are actually the same
character, and, in fact, there are only two central characters in this excellent example
of a dramatic monologue.

The principal character is of
course the speaker of this poem, who is shown to be a character who is obsessed with his
lover, Porphyria, and quite literally insane. He is in love with Porphyria, but reacts
violently when told that Porphyria is not able to be with him because of the way she
would have to reject society and the demands that it placed on her. Note how he reacts
to possessing her utterly for one last time before she will leave him
forever:

That
moment she was mine, mine, fair,

Perfectly pure and good: I
found

A thing to do, and all her
hair

In one long yellow string I
wound

Three times her little throat
around,

And strangled her. No pain felt
she;

I am quite sure she felt no
pain.

Possessing her utterly
is something that he never wants to end, and so he decides to kill her so that he can
gain eternal possession of her and she can be "his" forever. Note the way that he
deceives himself in the last two lines of the above quote into thinking that she felt no
pain when she was killed. The narrator is therefore an incredibly disturbed
individual.

The only other character to feature in this
poem is Porphyria, who is blonde and beautiful, but also who rejects her lover and her
emotions for the sake of society and the expectations placed upon her. However, at
various points, her emotions overpower her and force her to meet with her lover, and
this is what brings her to the speaker of the poem on this fateful night, when her
inability to be with him forever will ironically lead him to kill her in order to
possess her.