Riddle 37

In gorgeous splendor, once upon a time
My second reigned in Afric’s sunny clime;
A slave provoked his monarch’s royal ire,
And stood before him under sentence dire.
“My first, my last,” he stammered, “pity me!
Must I obey thy horrible decree?
Oh, thou who over millions hast control--”
One word the magnate uttered, ’t was my whole.