The Elven wizard Teclis once observed a Sigmarite Warrior-Priest performing his Miracles, and noticed that the power was not coming from an external source, but that the priest was unknowingly manipulating the Winds of Magic into the forms of his faith.
You are conscious of this fact, and can use the Winds of Magic to replicate the Miracles of the Old World's Pantheon. You can heal like a priest of Shallya or a Grail Damsel, enhance your wisdom and skill like a priest of Myrmidia or Verena, and enhance your strength like a priest of Sigmar or Ulric.