It couldn't be. Narcissa was lost, first to war and then to Bellatrix. As much as he'd disapproved of his son's choices in the last few years, he had agreed with Draco that cremation was the only way to ensure that the woman they had both loved would be at peace.
And now, seeing a phantom with her shape, her voice, her beautiful face and perfect form -
"Narcissa?" He raised his hand, oblivious to the battle raging about them. There was an edge in her voice he didn't remember. "Why are you here?"