The subject is a free interpretation based on Gandalf's sword Glamdring, an elven forged blade from the former city of Gondolin. Like so many of these swords, Glamdring glows when orcs approach and, deep underground, the shadows of these creatures hover on the passage wall.
The scene occurs during Bilbo's journey through the ways under the Lonely Mountain. Gandalf calls a halt at a sharp bend, to ambush the pursuing orcs. The orcs stop and then flee at the sight of the much-feared Glamdring, called Foe-hammer or Beater by the Hobbits. But in this instance the wizard was not accompanied by Legolas, the elf and Gimli, the Dwarf. The painting is also inspired by the journey of the Brotherhood of the Ring, eighty years later, which included Gimli and Legolas, as they marched through the abandoned mines of dwarf kingdom of Moria.