Fires when a unit loses or gains a buff or debuff.. This event fires before the effect of the buff can be seen on the character. For example if the unit gains the Mark of the Wild buff, at the time this even fires their stats may not have updated to reflect the gain from the buff. If you wish to be notified when the buff effect is gained or lost, register for the event that tracks the attribute being affected (e.g.
unitID- The unit that was affected. (