These formations are neither natural nor sculpted, they are, in fact, real trolls turned into stone many years ago by Bilbo and his company.
After being stabbed by a Morgul blade, Frodo is slowly slipping into Shadow; he is in need of Elven medicine. In their rush to Rivendell, hoping to slow the poison, Strider stops here and, through darkness and foliage, they search for the athelas plant.
