I must have missed a line or three early in the expansion, because at some point we learn that everyone blames Ardbert's party for the flood, Ardbert included, and I have no clue why.

From what I can gather, the First getting threatened by light has been going on for some time now. Eventually Ardbert's party was approached by the Ascians, who tricked them into coming to the Source, thinking that killing us would save their world. Instead we kick their asses and they go back to the First together with Minfillia.

So far so good, but what about all of this caused the flood to happen, and why does everyone on the First know that Ardbert's party is at fault?