This is a Spriggan, a very apt goblin for megaliths, as he seems to be made out of rocks and looks like one of the Cornish Tors. The Spriggans led humans to believe that they were the ghosts of giants, they are the guardians of hill treasures, such as that found in the old barrows.
All Hallows, when the thin veil of time is split asunder and the dead come back to visit their family or tribe, and sometimes, just sometimes, they take back the living with them to their spectral homes. Yes, All Souls/All Saints night, that time when paganism and christianity meet on the same date. Samhain it is called in the pagan world, a time of festival, of slaughtering the surplus beasts for a great feast before the famine of winter looms large. Apples gathered, the wheat safely harvested, the spirit still whirls into our modern time, a thanksgiving for the harvest of the year.
It is the time when we look back into the past and invite the dead to join in the revelry, the time when we tell our children terrible tales of ghosts, and towns under the sea such as Dunwich when the old church bell tolls beneath the sea. Of the dead walking through the streets from the graveyard to knock on our doors, don't open though, you may not like what you see, and skeleton fingers are very strong.
And what prompted this rash of words you may ask, well it was that old Faerie book with its drawings of Bogies and Spriggans, it captured those rather dreadful fairy stories I used to read as a child, not the nice fairy but wicked creatures who set out to torment you a bit like Christina Rossetti's Goblins....
This is a bogie, a shape shifting creature