Gawain and the Green Glass Knight

For Rustin, who had a dream that was kinda sorta like this.

A modern-day Gawain once met a knight
whose flesh was made of glass, all bottle-green
a robot built for war, a fearsome sight
a vacuum-hearted warrior death machine
whose blade was diamond-edged, as keen
as fine-knapped flints. Gawain fired his best shot,
coherent sound, a sonic hammer peen.
The knight just grinned. "O fool from Camelot,
my heart is well-removed, and I am not
to be destroyed by mortal means. Gawain,
commend your soul!" "Methinks this calls for brain,"
Gawain replied, and dived into the spot
between the sofa cushions. Reader, note:
Green Knight's a slave, Gawain found the remote.