Here's what a bloodline is basically like in the game. I've done three so far (this, vampires and lycanthropes), but you probably get the idea. The first two weaknesses are usually roleplaying oriented, while the last is
Auras of the Dead
You can sense dead spirits in the area, and can often speak to them. Due to the closing
of the Well of Souls, ghosts are in abundance and often hang around their bodies for long periods of times.
Three times a day, you can peak into the veil of death and see if there are any ghosts or spirits nearby.
These spectral creatures can see into the real world, so you can ask them a question or two before they
become distraught or depressed and no long wish to speak. You can also sense emotions of a person or place, such as telling if a place or body is tainted with violence or sadness.
Weakness: You feel like you have a purpose to fulfill, but you do not know what it is. It could
be to reconcile with someone, to create something or some other mission. You will do almost anything if
you think it could potentially help you in your mysterious quest.
Hide in the Crowd
You can not turn entirely invisible, but you can get damn close. Three times a day, you can
magically turn yourself nigh unseeable, granting a +4 bonus for opposed stealth checks for 10 minutes. You can even pick up objects and manipulate them, giving the sense that they are possessed. However, if you attack someone, they instantly know where you are and the penalty no longer applies. You could also be revealed by something being thrown on you, like paint or flour.
Weakness: Your skin turns cold to the touch, and you look as if you are hypothermic. The air around
you is cold as well, meaning very few people will want to be close to you for any extended period of time.
You can turn parts of your body insubstantial, allowing it to phase through objects as
if they weren't there. You can do this three times a day, and can phase through any solid object, including
bodies. If you make a difficulty 13 athletics check, you can phase your whole body through an object.
Weakness: You can easily be driven from a place ala an exorcism. While the exorcism does not harm you, if it is successful you can not enter the area for at least 24 hours. Powerful exorcisms can bar you from a place for decades if they are done right. Exorcisms are a Mental Effect Save, though the priest/exorciser must actually be trained in exorcisms. Every 2 points under your roll adds a unit of time i.e. if you fail by 2, you are barred for a day; by 4, barred for a week; by 6, barred for a month; by 8, barred for a season; by 10, barred for a year, and so on.