I am not quite sure what you mean.

If you mean what the dragon is actually holding, like a pearl in this picture, then you would say “Que tient le dragon ?” or “Qu’est-ce que le dragon tient ?”

However, if you mean a treasure or something that the dragon would be guarding then you would say “Que garde le dragon ?” or “Qu’est-ce que le dragon garde ?”

In both cases, the first sentence is much better than the second.

If you mean something else, let me know in the comments.