WoD is in the Void?

[KarstenS]

We did sort of. He was breaking free of his seal and corrupting the city around him. That's why the elementals got into a panic and we were tasked with finding out what evil was stirring in there. In order to get to Diabolos though we had to break the seal entirely. We thought we'd killed him in his weakened state but in fact he'd turned into a swarm of bats and escaped. He would have escaped eventually anyway but we did technically hasten the process.

Historical Amdapor is no requirement for Void Arc.

There is a slightly difference in the dialog with Cait Sith afterwards. But he is in the Arc even without doing historical Amdapor before.

So we are not the reason Diabolos got out of his seal.

[Alberel]

Historical Amdapor is no requirement for Void Arc.

There is a slightly difference in the dialog with Cait Sith afterwards. But he is in the Arc even without doing historical Amdapor before.

So we are not the reason Diabolos got out of his seal.

I was quite explicit in my post that he would have escaped eventually regardless of our presence. I merely pointed out that in order to reach Diabolos in Amdapor we had to break the seals on his prison. We quite literally smashed them all as we made our way down the platforms in the final part of the map. The entire reason we were sent there was because Diabolos was breaking free so we released him with the intent of destroying him; instead we only severely weakened him and he escaped.

By the continuity of the game assuming you have played everything that comes before we DID free Diabolos. That is the canon story, regardless of whether you personally cleared the duty prior to the Void Ark.