Marionette

Marionettes are sometimes used by necromancers as a means of housing the ghost of particularly valuable assets they've discovered.

They do this as a means to ensure that they can't escape back into the nether, never to be seen again.

While bound to such a body the necromancer can poke and prod at them for to learn all of the arcane knowledge they have to offer.

Particularly powerful entities can actually animate their new forms and have been known to even slay their captors should they let their guards down.

In later centuries these forms became a basis for new cybernetic tech used to house the critical components for life. The tech would eventually give rise to Panzer cyborgs in the distant future.