The darkness inside

I’ve heard of the dark and light we’re given
Two odds, battling ferociously within
But the grey line between death and wisdom is thin
And many will give in to this black sin
If this darkness infects us, we will never know
A silent killer, with not but a flinch as it grows
There is no light to defend our fragile soul
Through veins unclean, this black blood begins to flow
With this darkness inside of us, no light will ever show