# Are the effects of a power applied in an “atomic” mode?

Are the effects of a power applied in an "atomic" mode, i.e. all at once, or are they sequentially applied ?

So for example, the power says … "does 1W + Int damage and pushes the target one square" ... and the target has an Immediate Interrupt schtick … "on taking damage, teleport 5 squares"

Does the target's schtick happen in between the damage and the push?

Individual phases of a power are atomic.

In your example, "do 1W+Int damage and push the target 1 square", the damage and push are linked: when the attack impacts you, it both damages you and shoves you simultaneously. An immediate interrupt would take place before both of them, while an immediate reaction would take place after the both of them.

Some powers, however, have fairly obvious "phases", where events take place in sequence, as discussed in this question for example.

As the RC (p92) explains:

The order of entries in a power description is a general guide to the sequence in which the power's effects occur. For instance, an "Effect" entry might appear before an "Attack" entry to show that something happens before the attack.

Thus targeting a creature with an attack is one phase, making the attack roll & determining a hit or miss is one phase, and applying the effects of a hit is one phase; that's why each of these can trigger an immediate action. Some example triggers: "You are the target of a melee attack," "you are hit by a ranged attack," "you take damage".

Consider the barbarian power Hurricane of Blades, PHB2 pg60:

Target: One creature
Attack: Strength vs. AC
Hit: 1W + Strength modifier damage
Effect: Make the attack five more times against the same target or different ones.

Each attack is atomic, but the power as a whole is not. Suppose Barbarian Bob uses Hurricane of Blades while fighting a single enemy. If that enemy uses an Immediate Reaction power that triggers on taking damage after the first attack to teleport away, the remaining 5 attacks are wasted. The reaction takes place after the first attack resolves, not after the entire power resolves.

Note that movement is never atomic: each square moved is an individual event.
From the RC, pg196 (emphasis mine):

Likewise, an immediate reaction can interrupt movement. Here's how: If a creature triggers an immediate reaction while moving (by coming into range, for instance), the reaction can take place before the creature finishes moving, but after it has moved at least 1 square. In other words, an immediate reaction can be in response to a square of movement, rather than to an entire move action.

• So what happens in the specific example, out of curiosity? It is pushed and then it teleports seems to be the conclusion. I've also been looking for any immediate interrupt triggered on 'takes damage' that isn't a variation on 'reduces damage taken', and there don't seem to be any, which makes me wonder if the whole point is moot. – Ananisapta Jun 17 '12 at 18:53
• I think interrupts actually occur before the entire attack process. In the example above, you would teleport, and then if the attack is still valid you would be pushed and take damage. That's how the RC describes interrupts at any rate. It doesn't fit with the RC's description of events happening in sequence, though. Maybe that's why there aren't any interrupt powers that trigger on damage taken that let you escape the attack? Because powers to escape entirely ought to be triggered by the attack roll? – Oblivious Sage Jun 17 '12 at 19:21
• Actually, when it says entries are a sequence of when things happen in the power, it might be easier to treat each attack as a single event; it's only in multiple entries (Target, Attack, Hit, Miss) to make it more readable. – Oblivious Sage Jun 17 '12 at 19:27
• Different interrupts kick in on different parts of the sequence - being targeted, rolling an attack, hitting, taking damage. Strangely, powers like Shield are 'on hit', but their effect is to make it harder to hit. It appears that the sequence is actually retroactive, undoing events that have already taken place, in a weird, branching time-line kind of way. That is, a hit is registered, Shield activates, the hit is de-registered again in a way that made it not happen in the first place but which still activated the trigger. – Ananisapta Jun 18 '12 at 0:41
• Yes, that's how interrupts work: they take place before whatever triggered them, and can potentially prevent their own trigger. – Oblivious Sage Jun 18 '12 at 0:52