My guesses.
[spoiler='5. It cannot be seen, cannot be felt, Cannon t be heard, cannot be smelt. It lies behind stars and under hills, and empty holes it fills. It comes first and fools after, Ends life, Kills laughter.
']Dark
[spoiler='8.This thing all things devours: Birds, beast, trees, flowers; Gnaws iron, bites steel; Grinds hard stones to meal; slays kings, ruins town, and beats high mountains down.
']Time