Bondage witches have developed their mystical powers to compensate for the physical restraints imposed on them. Some may have exhibited supernatural talents before becoming bondage victims, but the desperation and physical helplessness brought on by prolonged bondage is the root of their power. They channel the energy they can't use physically into mental powers.
Limitations
Echoes
Bondage witches are not fully in control of their powers. Small abnormal events are common around them, especially when tired. Psychic whispers, involuntary mind reading, poltergeist activity, a visible nimbus or aura. A combination of anxiety, lack of concentration, subconscious urges, and fatigue can cause them to go wildly out of control and even completely take over the psychic, turning her into a creature of mindless impulse.
Geas
Bondage witches need to be physically restrained to work their magic. When they are not restrained, they lose their focus as their Chi is channeled to the body and not into magic. The degree of restraint needed varies, more advanced magical operations require more extreme bondage. Everyday combat magic require only simple arm bondage, while advanced rituals like astral questing require a full body restraint complete with gags and blindfolds.
The flip side of the coin is that a bondage witch never suffers any penalties to her Sorcery because of bondage. She may be unable to act physically, and being blinded or deaf can make it hard for her to notice what is going on around her, but as long as she can locate targets (by touch or divination, for example), she suffers no Sorcery penalties. Of course, she still suffers all normal Impairments on other tasks.
Common Schticks
Summonables
Bondage witches bring things into existence from their own subconscious - terrible nightmares out of their own twisted dreams. These are formed by the stories and superstitions they grew up with, and thus often confirm to local expectations. A bondage witch can use regular summoning lore from other magic traditions.