Affliction is a physical, exotic advantage described in Basic Set, p. 35-36, and referenced in GURPS Powers™, pp. 9, 17, 21, 31, 39-41, 118, and 169. Affliction is subject to a wide range of enhancements and limitations and is often used to build superpowers or other unnatural effects, and is the base advantage used to build 'buff' style powers that benefit your allies.