lifeblood

noun

Etymology: From life + blood. Compare English heart-blood (“lifeblood”).

1. Blood that is needed for continued life; blood regarded as the seat of life.

   “[Y]ou desire his mana, yet you respect his tabu, for in you and him alike runs the common life-blood.”

   “You didn't come to me in time. And by the time you came to me that fool of a doctor had bled and leeched the lifeblood out of Timmy.”

2. That which is required for continued existence or function.

   “Gasoline is the lifeblood of the modern city.”

   “Information is the lifeblood of the United States and the world.”