This is a very clever interpretation of two scenes from The Hobbit with a thematic link to them. Plus the builder has used custom LEGO minifigures rather than the official ones.
At the bottom we have Thorin and Gandalf meeting at the Prancing Pony and stating their need for a burglar. Then up top we have Bilbo in the Lonely Mountain hunting for the Arkenstone.
Source: MOC Pages — Which is why we’re going to need a burglar