DracoSuave
First Post
Don't have time to use a more official source, but from the Heroes of Shadow promotional material:
Dungeons & Dragons Roleplaying Game Official Home Page - Article (Necromancy & Nethermancy)
This would not be the first time that promotional material talking about the game would be incorrect regarding how the game feature works.
If that's how it is intended (which you're right, it probably is), that is not how it is written, and that is not how it works as written. This is one of those cases where the power could easily have been written to reflect that intent.
There's no excuse not to.
It's not a sustainable spell, which implicitly last for an encounter, no more. It has no duration listed other than the 0 hit point one. If you want to convince him, you should provide the rule that says otherwise.
Ie, summoned creatures general rule: "Duration: The summoned creature lasts until the summoner takes a minor action to dismiss it or until the end of the encounter." Except, this one implicitly has another duration, which is more specific.
Much like it deals your surge value instead of half your bloodied value, if you have no surges and it dies, unlike normal summoned creatures.
Again, adding additional conditions for a power to end does not erase previous conditions unless those conditions are impossible to meet otherwise.
Nothing in the power says that it can last beyond the end of the encounter, so the keyword's rule does, in fact, apply, same as any other rule in the game that does not have a specific exception.
Draco's Corrolary: "When an exception to a general rule does not actually exist, you apply the general rule. That's why they exist."