Answering the questions that were asked first assuming
Team of Ambassadors is played normally*, but will expand afterwards:
Takket wrote:Can I still play this interrupt to nullify the dilemma even if my opponent has already killed someone with the dilemma?
Yes, but only if you fail to meet the requirements and encounter the dilemma again later.
Takket wrote:If I do... does the person that was killed "come back to life" from my discard pile and rejoin the attempt?
No. Nullifying the dilemma on a separate encounter would not return any personnel it killed on previous encounters.
So the timing goes like this:
Reveal
Misinterpret History
MH encounter initiation step: kill target chosen. (note: nobody is killed now)
MH encounter response step: either player may make valid responses now, this is when Team of Ambassadors could normally* be played to nullify the dilemma.
MH encounter results step: target is killed, and if requirements are met dilemma is discarded or if requirements are not met dilemma is reseeded.
* It occurred to me that
Soval has a special download of
Team of Ambassadors after writing this. You could use this download during the results step after the personnel is killed. In that case I would probably lean on the glossary passage that Jebus quoted and treat the dilemma as though it were nullified during the response step.