Speaking with Long Dead People

[Bromley20]

In the Eberron campaign I'm playing in, there was an incident a little over 100 years ago that led to the assassinations of almost every head of the dragonmark houses. Cannith was blamed for the attack since they weren't targeted. Everyone that was part of the house was hunted down and killed or forced into hiding in the wilderness. I would like to question the people that were killed and the people who were blamed then killed as a result. I want the other side to the story. Right now all I have is the word of the people going out and murdering ever Cannith member they find. I don't necessarily trust their word because the accusation was made by 1 single person. 1 good lie at the right time could have started this whole genocide.

Is there a spell that can summon a petitioner from their afterlife to be questioned about the incident? If not summon them, at least question them in some way. I know speak with dead could theoretically be used to get the info but it requires the mouth of the body to be at least somewhat intact. I can't guarantee that it would be after a century of decomposition. If needed, I may have to resort to casting resurrection on everyone before questioning them. However, that requires everyone to be willing to return which I also can't guarantee. I just want to find out what really happened during that time and confirm the accusation or clear their name.

[Telonius]

Contact Other Plane or Commune could get you the information second-hand. (The deity in charge of the petitioner's afterlife would be a good first stop). Legend Lore is a less certain option, since there may have never been any alternate stories about what happened, but I think there's a case to be made that it could give you a clue.

Stone Tell is another (limited) possibility, if the incident happened in a stone structure that's still there.

[Zombimode]

Contact Other Plane or Commune could get you the information second-hand. (The deity in charge of the petitioner's afterlife would be a good first stop).

There is not such thing as a "deity in charge of the petitioner's afterlife" in Eberron.
It is questionable if there are petitioner's in the usual sense at all in Eberron.

[sleepyphoenixx]

Hindsight might help, or Sensitivity to Psychic Impressions if you have a Seer on hand.
Otherwise if you can get your hands on something the dead carried on them when they died Soul Shackles (BoVD) might work, but it's evil and not written very well.

[Bronk]

I know speak with dead could theoretically be used to get the info but it requires the mouth of the body to be at least somewhat intact. I can't guarantee that it would be after a century of decomposition.

If you can find the body, the level 0 Mending or the level 2 Make Whole would help.

[ixrisor]

The nuclear option is, as always, Teleport Through Time, which I can’t link to but is the first thing to come up if you search it.

[tiercel]

I just want to find out what really happened during that time and confirm the accusation or clear their name.

Hindsight (Brd 6, Sor/Wiz 9, SpC) would indeed do the trick (as sleepyphoenixx pointed out), not by talking to those long dead, but by seeing and hearing into the past, as long as you are at the location the event happened. Of course, finding someone who can cast the spell or sell you a scroll could be a quest in itself, to say nothing of how Interested Parties might react if and when they discover your intentions....