The emperor has lost his imperial orb. The two Deaths are tugging at the emperor and his crown. Holbein took the picture of Death trampling on the emperor's orb from his earlier work - the Holbein dagger (picture to the left).
The accompanying text for this letter goes: »Bereyt dyn huß / wan du würst sterben / vnd wurst nit leben. Da wurst du sterben / vnd do würd syn der wagen dyner glory«.
The first part is Isaiah 38,1 which in Luther's translation sounds: »[...] Bestelle dein Haus, denn du wirst sterben und nicht am Leben bleiben.«. In English: »In those days was Hezekiah sick unto death. And Isaiah the prophet the son of Amoz came unto him, and said unto him, Thus saith the LORD, Set thine house in order: for thou shalt die, and not live«.
The second part is Isaiah 22,18, which is rendered thus by Luther: »[...] Dort wirst du sterben, dort werden deine kostbaren Wagen bleiben, du Schmach für das Haus deines Herrn!«. In English: »He will surely violently turn and toss thee like a ball into a large country: there shalt thou die, and there the chariots of thy glory shall be the shame of thy lord's house«.
Notice that the Bibles don't quite agree: With Luther the chariot shall remain (German: bleiben) and the poor person who has to take all this abuse is called "thou shame of thy lord's house". In King James' version, the chariot in some mysterious way becomes the shame of house.
To the left is a copy designed by Hollar.