The Unbound

Playing a Ghost
A ghost would be a challenging, but not impossible character in the world of darkness. Only able to interact with other ghosts and Sin-Eaters (for the most part), tethered to places or things, and having only limited powers and ways to regain them are among the tougher prices to pay. On the other hand, Geist is a game of second chances, and a ghost who has "awakened" into a second sort of life can easily fit into the chronicle. All ghost characters possess the Lucid Dead Numen (Mummy the Curse, p. 209). In short, this means that a ghost is built in the same way as a living mortal, rather than use Power/Finesse/Resistance. Such a character begins play with three additional numina and two anchors of the player's choice. Possible Numina are listed here: List TBC

Playing an Unbound Human

 * There is a merit in Book of the Dead called Gatekeeper (page 51). It is available at character creation, and allows a mortal to open up an Avernian Gate with little more than a touch and a whisper.
 * There are other merits from the same book that would make for an interesting mortal. Medium lets you see ghosts, either all the time or while under stress (at 5 and 3 dots, respectively). It also grants a price break on Unseen Sense. The other merits of interest is Beacon of Life, which grants your character protection from ghostly abilities.
 * If the Unseen Sense merit is attuned to Ghosts or the Underworld, the character can sense the presence of gates to the underworld.
 * Anyone can learn Ceremonies. A useful non-Bound character could help the party by focusing on learning these deathly rites. Such a character might be a scholarly individual - appropriate skills and merits could make the character a huge wellspring of knowledge on the death rites and legends of various cultures, helping the party by proxy while on their visits to the underworld. A non-Bound who learns ceremonies would use Morality instead of Synergy and Conviction instead of Psyche.
 * Conviction is the "Mortal Power Stat" presented in World of Darkness: Mirrors. Its main use is to allow a heroic mortal to keep up with supernatural characters. It doesn't give access to any cool super powers, but it does let you even the playing field with sheer tenacity - a staple of the "Bad-Ass Normal" characters in fiction.
 * Most ceremonies don't use plasm - which is why a non-Bound could use them. However, a few of the higher-level ones do. Normally, a mortal would not be able to perform these ceremonies, but that said, there's nothing stopping a mortal - especially one so entrenched in the occult - from acquiring a Deathmask. Using it may come with risks (say, sanity), but nothing really  stops  the character.
 * The character could be a Thaumaturge or a psychic. Vodouns and Mediumists (respectively) deal with ghosts and the dead almost exclusively. While they would have to spend XP to get a number of things that Sin-Eaters get for free, they also gain access to a number of potential abilities that Sin-Eaters can't possess.