[johndallman]

Dependency [-1 to -175] is an exotic physical disadvantage. Your health and life are dependent on something external: you need to consume something unusual, have physical contact with a special object, or visit a specific place at regular intervals, and if you don’t, you take HP damage. This can kill you.

The cost of Dependency is highly variable, depending on how unusual the substance, object or place is, its legality, and how often you need it. The latter also determines how often you take damage, and how long you need to spend using whatever you’re dependent on.

Dependency isn’t the only way to represent special life support requirements: Maintenance and Restricted Diet can also be used for that. Doesn’t Eat or Drink, Draining, Increased Life Support (which is about logistics, not health), and Terminally Ill can also be connected to this disadvantage. With the Aging enhancement, Dependency can also be used for people who age rapidly without access to something special. While this is normally an exotic disadvantage, it can be used with the GM’s permission to represent mundane serious medical conditions, such as the need for special drugs or a mechanical ventilator. It appeared during the 3e period, apparently in Supers.

There are a wide range of things to have Dependency on in GURPS supplements. Widely-used ones include “Mana,” with many variations, “Sunlight,” “Water” and “Alien Atmosphere.” Odder ones include “The environment that caused my mutation,” “My vessel’s body,” “Blood of sapient beings,” “Commercial hormones,” “Anti-rejection drugs,” “Kidney dialysis,” “Toxic Waste,” “Sanctity,” “The area I’m responsible for,” “Rest in own tomb,” “My grove,” “Animal flesh,” “Coffin with soil of homeland,” “Grave goods,” “My kingdom,” “Own, non-decapitated, corpse,” “Sexual energy,” “Fear,” “Life energy,” “Creator’s will or desire,” “Funerary Amulet,” “Infant’s Breath,” “Luck, via Curse,” “Plot-device formula,” “Cave environments,” “Broadcast power,” and the good old “Weird Energy.” If an Alternate Form is meant to be very tiring or draining to use, that can be represented with Dependency on the normal form, probably with Fatigue Only (-50%).

There’s a character in my Infinite Cabal campaign who has Dependency (Mana, Weekly). He’s never been stuck anywhere without mana long enough to take damage, but it’s a constant background threat. What has Dependency done in your games?