Generally, ghosts are non-sentient and nigh-useless spirits in the world, but there are a few amazingly rare exceptions. One such exception can be found in the grateful dead spirits that some shapeshifters are able to call upon, referred to as 'Munin' by many Lukoi packs (and by other names by other packs of shifters, as well as a few other non-traditional Lukoi packs).
The process by which a Munin is established is fairly straightforward — the corpse of the fallen shapeshifter is consumed by their pack-mates, and thus the pack is able to call on the departed for advice and assistance. The consumption itself isn't a milquetoast sipping of an ounce of skin after it's been boiled in a five gallon pot, but instead requires an act of eating that clearly demonstrates one's devotion to the deed (generally involving at least eating parts of the deceased's brains, liver, and/or heart). Once consumed, the departed shifter's spirit can not (or will not) manifest to the pack for at least three days post-death, and not until the next full moon has passed since the eating.
To possibly call on a given departed shifter at any time or place, one must have actually taken part in the eating of that departed shifter. If the pack has established a burial ground for the bones of their departed (that have been 'saved' as Munin by some members of the pack), one can attempt on a full moon to call on those buried there (presuming one is a member of that pack and has the ability to Channel Munin), even if one has not specifically eaten of the Munin one is attempting to call.