"now he lies writhing on his black bed in the room like a Mycenaean tomb"

The Tomb of Agamemnon
Creative Commons AttributionThe Tomb of Agamemnon - Credit: Carlos M Prieto
 Mycenaean Greece was a Bronze Age period lasting (approximately) from 1000-1600BC.  Many of the ancient Greek myths and literary adventures (such as Homer’s epics) were later believed to have taken place during this era.  At some stage, the Mycenaean began constructing tombs in which to place their dead, with the grandest reserved for royalty, such as the House of Atreus.  The Tomb of Agamemnon, also known as the Treasury of Atreus, is a ‘tholos’ beehive shaped structure, located at Mycenae itself.  It is judged to be the finest example of the period, with a height of 13.5m and a diameter of 14.5m; the lintel stone above its entrance weighs 120 tons, and remains the heaviest in the world.  Carter seems to be invoking a similar sense of grandiosity by using description in relation to the Duke.