Answer:
What is neither inside the house nor outside the house but a necessity for any home?
A horrid monster hides from the day, with many legs and many eyes. With silver chains it catches prey. And eats it all before it dies. Yet in every cottage does it stay. And every castle beneath the sky.
I never was but always will be. No one ever saw me but everyone knows I exist. I give people the motivation to better themselves every day. What am I?
It is sometimes known to have silver linings.
I build up castles. I tear down mountains. I make some men blind. I help others to see.
I have two eyes in the front and a lot of eyes on my tail