This gruesomely beautiful decaying deer skull is indeed an extremely well crafted piece of sculpture cast in resin. As you can see from the detail shot, there is also some mysterious ship and motif with further script writing underneath. This deer skull, called Ne Plus Ultra,

If you have no idea what 'Skull Corpsing' is then you are not alone but with a little time to linger on it we're are you would have worked it out. 'Skull Corpsing' is when you take a skull, well a  replica of a skull