I think the history of Arkand text has been cut down from some original manuscript, and there are points where it shows.
Page 6: "But the pirates’ greed and uncompromising pursuit of
freedom fed the demonic influence beyond the sea floor.
After two dozen years, the demons launched a concerted
assault to break free from their captivity. The seabed shook
and the ground gave way. A huge tidal wave swept across
Arkand, washing away all life. The age of pirates was over.
At the bottom of the sea, the draconic seal still pulsed
with power, unbroken. Beyond it lurked the demons, bitter
and diminished."
It's pretty unclear if the demons caused the tidal wave or somehow the magical seal was the reason. And the relationship between the pirates and the demons is also a little weak. I'd change the order and wording a bit:
"But the pirates' desire for absolute freedom and their limitless greed fed the demonic forces beneath the sea floor. After two dozen years, the demons felt strong enough to challenge their captivity. They threw themselves against the draconic seal with such force the seabed shook and the ground gave way. A huge tidal wave swept across Arkand, washing away all life, ending the Age of the Pirates.
But the demons had failed. At the bottom of the sea, the draconic seal still pulsed with power, unbroken. Bitter and spent, the demons still lurked in their magical prison."
