Forbidden knowledge
In image alone
Chains are false warning
For concepts unknown
Scribed in the dark
And valued in the middle
Now dangle in the modern
Can you solve my riddle?

HINT #2: Lines 5, 6, and seven all should have one word tacked on the end, to complete them. Therein lies the word game.

I would like to add that this is not a riddle about a navel, or a hairdo, or an arbitrary, useless thing. It is quite useful, yet also of little use.