[Note: The Codex Immortalis is a document in Italian which is available in full here. The documents below are English translations.]
Codex Immortalis: Volume One
Chapter 2: Immortals of Mystara, from The Piazza posted 14 October 2008.
Chapter 3: Priests, from The Piazza posted 10 October 2008.
Appendix 1: Index of the Immortals by Sphere, from the Mystara Message Board posted 28 March 2007.
Appendix 2: Alphabetical Index of the Immortals, from the Mystara Message Board posted 24 March 2007.
Appendix 3: Hierarchical Index of Immortals, from the Mystara Message Board posted 28 March 2007.
Appendix 4: List by Name or Nickname, from the Mystara Message Board posted 19 April 2007.
Appendix 5: List by Areas of Interest, from the Mystara Message Board posted 24 March 2007.
Appendix 6: List by Domains, from the Mystara Message Board posted 16 March 2007.
Appendix 7: List by Alignment, from the Mystara Message Board posted 11 August 2007.
Appendix 10: Player Lists of Immortals, from the Mystara Message Board posted 06 April 2007.
Appendix 11: New Cleric Domains, from the Mystara Message Board posted 10 March 2007.
Codex Immortalis: Volume Two
Chapter 4: Religious Organisations, from the Mystara Message Board posted 27 October 2007.
Chapter 6: Pantheons, from the Mystara Message Board posted 21 November 2008. UPDATED
Chapter 7: Groups of Power of the Immortals, from the Mystara Message Board posted 11 August 2007.