Seele - Soul
Seelen - Souls

Über - Over

Unter - Under

The Überseele, or oversoul is seated in the brain. It contains the thoughts, memories, and personality of an individual.

the Unterseele or undersoul is seated in the heart. It contains the appetites, emotions and fears of an individual. 

Ghosts are thus bodiless überseelen, a spirit containing the thoughts, memories and personality of an individual who had passed on. In comparison, a poltergeist is an unterseele, that is to say, it's a bodiless spirit fueled entirely by appetite, emotion and fear. Not every variation of Seelen lacks a body. The shambling undead known as the zombie is a body lacking an überseele leaving a host completely devoid of thoughts and personality and only fueled by appetite and instinct. 

A Jäger could live their entire life without ever becoming activated, in which case they would nearly indiscernible from the average human. However once activated, the Jäger comes into possession of a second überseele. This second überseele is what grants a Jäger their ancestral memories, talents and in more extreme cases, personalities. 

A Magni is born in possession of a second unterseele. This second unterseele can physically manifest from a Magni's body, acting as their familiar spirit or animal guide.