Hi Jim,
I enjoyed this 'darker' poem!

I have some suggestions below for you to ponder as you wish.
Enjoyed!
~Cleo

Beware these eyes: grey-steel and poet-wise,
they see beneath your soul and find the faults,
Suggest ‘straight through’ for beneath. Also, would you consider subbing ‘the’ for something else? Or perhaps “and find the faults: frailties which redefine. These eyes chastise"the frailties which define. These eyes chastise
Got an extra beat here in this line – suggest ditching ‘the’ as mentioned above.the secret “you”, however many vaults
you built inside: no harbour here to hide
This seems awkward. Suggest something like ‘you build inside: no harbour’s left to hidefrom retribution. Other lashes pale
beside the ones I wield; old sins of pride
laid bare with every blink – assassin veils.
Nice!The centres drown: dark pits to pull you down
Suggest replacing ‘to’ with ‘shall’to Hell’s damnation. Light has lost this fight.
An inner Dark reclaims the victor’s crown
surrendered once but won back here tonight.
Suggest ‘surrendered once: victorious tonight.' I just offer this example as I try not to use the word 'but' if possible.Such bloodless battles serve to prove my claim
that Hell and Earth are only one domain.
I believe you need to swap ‘are’ with ‘is’?