Greater Possession
An extension of Lesser Possession, many versions of this ritual exist. In essence, it allows a merging of a living (umbral) spirit with the caster.
System: Both participants must be willing, and can (through an act of will) break the bond at any time. It takes four hours to cast, culminating at true midnight, and lasts for a period of time based on successes.
1 success: the rest of the night
2 successes: one additional night
3 successes: 3 nights
4 successes: one week
5 successes: one month.
Each spirit must be approached differently (the ritual re-crafted, the would-be summoner must roll Int + Occult = 8, achieving 25 successes, rolling once per year, or once per month if the appropriate spirit aids the research). The affect can be terminated early by the caster with a willpower roll, difficulty 8, each success soaks one of six aggravated health levels. The spirit must succeed in a willpower roll difficulty 9, and spend 10 power to break the bond. Spirits are aware, and can make themselves heard in desperate (to them) situations by succeeding in a willpower roll (difficulty of the host's willpower). In this case, the host is made aware of a quick thought, or forced to perform a reflexive action. True communication is possible through dreams or meditation. A spirit that accidentally violates its own chinmage or harms its paradigm is usually forced into slumber, so one who perceives that this might happen will usually break the bond quickly rather than risk this.
This ritual was originally created to mimic the horribly cursed being that is an Abomination. The storyteller and player should work out in advance what forms and powers this merging gives.