What costs more than riches?

What costs more than riches but doesn’t cost a penny; that’s also hard to find yet easy to lose? Check the answer here.

Money can be held in it

Not chest or box is now discussed. Money can be held in it, but just as we test its metal, within it there is rust. What is it? Check the answer here.

I’m the son of water

I’m the son of water but when i return to water, i die. Who am i? Check the answer here.