The Noble Charm (?)

[ScarlettO1939]

I bought this a while ago. I thought it would get my dragons to level 15! But do far it hasn't "done" anything at all!
Now can someone explain what this is really for please?

[[S8] Elsa]

The Noble Crystal will let you raise Dragons to level 15 when placed on your island. When a Dragon you are feeding reaches level 10, you will be able to continue feeding.