Redemption of Demons?
Some bits and pieces of trivia I gathered and you may find interesting on the              redemption of demons:
                  Saint Isaac the Syrian (7th century)wrote:
                  "What is a merciful heart? It is a heart that burns with love
                  for the whole creation — for men, for birds, for beasts,
                  for demons and for every creature." 
                  
                  
http://www.orthodoxeurope.org/theospirit/000013.php
                  
                  "The Spiritual World of Isaac the Syrian"
                  by Bishop Hilarion Alfeyev
                  Hilarion Alfeyev, The Spiritual World of Isaac the Syrian.
                  Cistercian Studies Series, Number 175. Kalamazoo MI and
                  Spencer MA: Cistercian Publications, 2000. Pp. 321. 
                  A cute story:
                  ...With the Sign of the Cross, the old monk Abba 
                  Joseph trapped in his cell a dark and miserable demon
                  who had come to tempt him. "Release me, Father, and let
                  me go," pleaded the demon, "I will not come to tempt you
                  again". "I will gladly do that, but on one condition," 
                  replied the monk. "You must sing for me the song that
                  you sang before God's Throne on high, before your fall." 
                  The demon responded, "You know I cannot do that; it will
                  cause me cruel torture and suffering. And besides, Father,
                  no human ear can hear its ineffable sweetness and live,
                  for you will surely die." "Then you will have to remain
                  here in my cell," said the monk, "and bear with me the
                  full struggle of repentance." "Let me go, do not force me
                  to suffer," pleaded the demon." "Ah, but then you must
                  sing to me the song you sang on high before your fall with Satan." 
                  So the dark and miserable demon, seeing that there was
                  no way out, began to sing, haltingly, barely audible
                  at first, groping for words long forgotten. As he sang,
                  the darkness which penetrated and surrounded him began
                  slowly to dissipate. The song grew ever louder and
                  increasingly stronger, and soon the demon was caught
                  up in its sweetness, his voice fully lifted up in worship
                  and praise. Boldly he sang of the power and the honour
                  and the glory of the Triune God on High, Creator of the
                  Universe, Master of Heaven and Earth, of all things visible
                  and invisible. As the song sung on high before all ages
                  resounded in the fullness of its might, a wondrous and
                  glorious light penetrated the venerable Abba's humble cell,
                  and the walls which had enclosed it were no more. Ineffable
                  love and joy surged into the very depths of the being 
                  of the radiant and glorious angel, as he ever so gently
                  stooped down and covered with his wings the lifeless body
                  of the old hermit who had liberated him from the abyss of hell.
                  AndyF