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.