What is a word for something that is protected or guarded? The thing that is being protected doesn't have to necessarily be valuable, secret, or even hidden from view. It just has to be something that is guarded, and difficult to access. The word must be a noun.

For example,

> 
> The King's horse was a \_\_\_\_\_. He allowed no one but himself to ride it.
> 
> 
> 

I would offer what I have thought of so far but I can't even think of a word close to it...