Xenoglosia

«El idioma de un extranjero» (del griego xenos==extranjero, glottis == lengua).

The voice of a demon that speaks through the mouth of humans, animals, or other beings.

A competent warlock can produce a trance to conjure a demon that can speak through the mouth to give any information he might desire. It may be possible to summon the spirit of a dead person through a medium.

This practice is incredibly dangerous for the being that acts as the mouth of the devil or spirit. The being may possess the body, or steal the soul, or remain in a dual parasitic state inside the host.