Remember the Sun

[Leanne]

You have some quite evocative images and you build the dark mood well, ending on a determinedly bright and hopeful note. There are a few phrases that could do with some work.

I walk through black sludge
That clings to my feet with haste, -- I'm afraid I can't reconcile the idea of sludge, which is viscous, clinging with "haste" -- you might consider leaving this line out altogether
Bites my weary sole,
And beckons me to relent. -- there is probably a better word than "beckons", which implies a gesture of some sort -- since you've already given the sludge teeth, giving it hands is really a step too far

The gray clouds simmer,
Churning anger and sorrow -- do they simmer or churn? One is quite a gentle action, the other violent
To pelt my soft flesh,
And wash all color away.

Dull lightning appears. -- I don't think this is a strong enough paradox to bother with. Personally, I'd drop this line and start with the next, maybe add in "charcoal lightning"
Charcoal streaks the oily sky,
Soundless and lonely,
Forsaken without thunder.

Softly, I whisper
Appeals that might go unheard. -- "might" is too low a modality, I'd make this more definite
For months unending,
Tomorrow will be today.

Trudge on sluggish knees
Across despair black as crows. -- bit of a cliche here
No, I will not cry,
For I remember the sun. -- nice idea, maybe strengthened by a colon after cry and dropping "for"