When does a creature deal damage? A number of powers mention "deals damage" and a number mention "takes damage" and a comprehensive understanding when, exactly, "dealing damage" happens would be useful.
For example, the level 9 Paladin Daily Power Shackles of Justiceddi specifies:
effect: Whenever the target deals damage, it takes 2d6 radiant damage (save ends).
I think it's fairly obvious that when the target attacks and deals damage, it takes 2d6 radiant damage from this effect. But what other things count as dealing damage?
If the target uses a burst or blast power and hits multiple creatures and deals damage to each, does it take 2d6 once for the power or for each creature it hits?
If the target has an aura, such as "any creature that starts its turn or enters the aura takes 10 damage" does the target take the 2d6?
If the target creates a wall or zone that deals damage every time someone enters or leaves it, does it take the 2d6 for each square entered?
If the target had applied ongoing damage before receiving the effect of Shackles of Justice, does it take the 2d6 when that ongoing damage is applied?
This one's actually quite a big deal, as Tacroy points out: what happens if two paladins use Shackles of Justice (or two creatures use similar powers) on each other; does this lead to an infinite cascade of damage?
Jon B. adds: when a creature summons another creature and the summoned creature attacks, who "deals" damage, the summoner or the summon? If the summoner has the Shackles effect, does she take damage when her summoned creature deals damage?
dpatchery adds: What about powers that force-move a target and the target takes damage as a result of that forced movement, such as pushing a creature off a cliff, teleporting a creature into the air, or sliding a creature into hazardous terrain? Do these count as "dealing damage" if the target takes damage as a result of the forced movement?
Please provide a broad definition of when and who deals damage in addition to addressing these special cases.