What is it? (3)

Written about in caves decades ago,

Drawn, scribbled and sketched.

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Passed down from generation to generation,

Absolutely essential for survival.

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More valuable than gold & diamonds,

For it people have lied, stolen and killed.

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However once obtained,

Never to be stolen or given away.

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Now you can work for it,

Common-place everywhere.

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Having it may set you up for life,

Yet be warned it can be like a two-edged sword,

Placing on you a burden you cannot bear.

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With its great power,

Comes great responsibility.

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What is it?

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The answer to Riddle (2) is Sickness.