Enigma 4

I was once on the brink of doom,

I rode the edge of disaster.

Now am I left delving in gloom,

in dread of what comes after.

Decisive moment: I stood ground,

a shriek flew at limit of sound.

Waist-deep in terrible rescue,

a mirror-lake, a deathly stew.

A shade of evil deeds stares back,

as if devising an attack.

Bearing myself upon darkness,

no chance hope or door to egress.

Demons haunt me at ev'ry bend,

now that I am damned end-to-end.

What am I?

Author's Note

Please refrain from posting answers/guesses. Thanks!