Mahabharata Sambhava Parva Section CXXI mentions an interesting story of a king Vyushitashwa who dies without siring any child. His wife lamenting on his death bed hears her dead husband's voice asking her to lay down with her on a certain day at a certain time:
Then she was addressed by an incorporeal voice in these words, "Rise up, O Bhadra, and leave this place. O thou of sweet smiles, I grant thee this boon. I will beget offspring upon thee. Lie thou down with me on thy own bed, after the catamenial bath, on the night of the eighth or the fourteenth day of the moon.' Thus addressed by the incorporeal voice, the chaste Bhadra did, as she was directed, for obtaining offspring. And, O bull of the Bharatas, the corpse of her husband begat upon her seven children viz., three Salwas and four Madras.
My questions are - Is this related to some Aghori or Tantrik practice? Are there any other instances of such impregnation of a wife by her dead husband in the scriptures?