Angst is what happens when an author gets it into his or her head that canon characters, who are not usually weepy and annoying, should be. It is generally the mechanism by which authors get unsuitable characters into each others' arms; this may be part of Hurt/Comfort. It may also be a reaction to hurt/comfort or being in the arms of an unsuitable partner. Characters that get bitten by the angst bunny frequently include all the usual suspects; Legolas, Harry Potter, Sirius Black etc etc ad nauseum. The Department of Angst's task is to cheer up these poor victims.