Journal of Vaven Cabal (Fall of Dum'Thol)

Today, the city fell silent.
My name is Vaven Cabal and this is my journal.
I've never been one for keeping such things, and I never thought I would. But the events that have transpired have spurred me to jot down my knowledge on paper. For without these words I fear none will ever know what has befallen Dum'Thol... that is, if this journal is ever uncovered.
For anyone who cares, I am an Okam'isa, born and raised in Okar. My father was a trade-ambassador to Dum'Thol on behalf of several of the city's corporations and as such I had a privileged, learned and Dum'Thol-centric education, groomed to follow in my father's footsteps. 
In recent years I have operated as chief logistics operator between the two cities. My father also possesses honourary Dum'Thol citizenship, which imparts on me specific privileges not afforded to other Okam'isa.
In recent days the city has been abuzz. No-one has truly acknolwedged it to me, or to one another, but there has clearly been something big planned. I was confident it was not invasion, nor anything overtly hostile to my fair home-city. Nevertheless, neither me nor the Dum'Thol'isa could have envisaged this.
At precisely light-tide the city went into absolute lockdown. Citizens were told to remain calm and all of my fellow Okam'isa were commanded to return to the lodgings. It would appear other senior dignitaries are holed up in the inner city, tucked away in ambassadorial and trade lodgings. I myself was running a trade errand in the Okam quarter and the guards permitted me to remain in the immediate area due to my status, although highly reluctantly.
I sat and I waited, and the guards stood and they waited too. Eventually, I heard the faintest of humming noises, nothing more than that which one gets when resting in the silence. But my Dum'Thol hosts were clearly greatly discomforted. They reeled, slowly and slightly at first, until they were soon contorting on the chamber floor. Then... silence. Every single one lay dead, and I have not a single clue why. What on earth befell my hosts? Why was I spared? A rapid and deadly disease? Posioning?
The city is sealed, the gates closed by Dum'Thol
yemol'nol okam'isa'nol a' sum