This thing all things devours
Birds, beasts, trees, flowers, gnaws iron, bites steel
grinds hard stones to meal
or
This thing all things devours,
Birds, beasts, trees, flowers;
Gnaws iron, bites steel;
Grinds hard stone to meal;
Slays king, ruins town,
And beats high mountain down.
Time
Riddle given to Bilbo by Gollum in The Hobbit.
Tolkien Gateway: Riddle-game