Word for something that is protected or guarded? Must be a noun

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...

Solution 1:

I would use prize. I know that you have not specified a contest, but prize captures both (a) a thing of value and (b) a thing worth striving for (and by extension, worth guarding until it is "won")

While prize is a noun, it may also be used as a verb, as in regard highly; think much of ("We prize his vast knowledge of words")

http://www.onelook.com/?w=prize&ls=a

Solution 2:

A ward is the responsibility of a guardian.

A charge has a more general connotation of a responsibility laid on a responsible person; what is laid in a charge could be a person or a mission.

A waif is a helpless child without home or friends.

You could also consider nouning an adjective like vulnerable.

In terms of things that are wrapped in a protective coating or envelope, you might think about payload or contents.

Solution 3:

Chattel might fit the bill.

• (in general use) a personal possession.
• LAW an item of property other than real estate.

(google)

. . . that is, if you don't mind one of the alternate usages:

• slave

(Merriam-Webster)

Even then, though, as 1006a commented, it's hard to nail down the "protected" part with using an adjective. Like . . . well, "protected".

Solution 4:

It's not typically used as a noun, but "coveted" is technically usable as a noun.