Half-Castes and Exaltation

The Scroll of Heroes book stated that the Blood/Essence of the Half-Caste already committed their existence to the service of their patron god.

This fly flat in the face of the Impersonal Nature of Exaltation and their Relationship to their Patron Gods.

So either the Celestial Incarna can block someone form Exaltation or they cannot.  You cannot have it both ways.

Thus Half-Castes can Exalt as something other than their parents.  The Essence in their being is meaningless.

This also means a Solar Enlightened Mortal can still Exalt as another Exalted Type.  So you cannot forever eliminate Sidereals by simply enlightening the world by using Solar Essence powered processes.