"Change, change, the form of man! Free the prince forever damned!
Release the might from fleshy mire! Boil the blood in heart of fire!
Gone, gone, the form of man! Arise the Demon --- Etrigan!" - Jason Blood

Quote taken from The Demon Vol. 3 #0 (October 1994)

History

  In the 6th century, the legendary mage Merlin (or Myrddin), himself the son of the demon Belial, made a pact with his half-brother, the rhyming demon Etrigan, to help him with various affairs concerning Camelot. At the time of Camelot's fall, Merlin bound Etrigan to the soul of a man named Jason Blood, making both of them immortal, but depending on each other, exchanging places on Earth and in Hell when the need arose. The double-life of Blood and Etrigan has endured to this day, and they were only recently separated. Because of Blood's human influence on him, Etrigan has been known as "the good guy from Hell". Though that epithet may not fully apply to him, Etrigan has often been more good-natured toward humanity than the rest of his demonkind - as long as it hasn't interfered with his own affairs. Just as often, he has shown himself to be a threat to mankind.