The witnessing actor, the acting witness.

A weariness within the bones
drifts somberly on a cloud.
It latches on keeps it grip,
fighting its own kind.

Poisoned hosts see not in,
but above and under eye.
Repel and rip the wounds
of they that shall not pass.

Mutation of this sorry pest
floats and sits asunder,
now only the witnesses that were never there,
can claim to need no cure.