Passive skills bestow a constant effect and are perpetually applied in the background.
Skills perform their function on their user and target, but they are also applied to their target's applied_skills
, a list of skill usages.
A skill naturally ends after completion. After all the keywords are complete, the skill will complete.
A skill prematurely ends if it is removed (the remove keyword targets applied skills) or reapplied (a duplicate skill ends earlier instances of the skill then is applied normally).
When a skill ends for any reason, all keywords must also end.