Guild Wars 2

What’s all this about acts? On here : https://forum-en.gw2archive.eu/forum/info/news/Update-Notes-October-22-2012, it says “From October 22 through November 1, Tyria is under the shadow of the Mad King. The weeklong event will unfold in four acts, each introducing new content to explore and experience.”, can someone expand on this?
Do I need to finish these acts for any achievements, and if I don’t will I not get the Emissary of the Mad King title?

I know they have to be done in order but what the end result is, who knows

We’re in Act I right now put it that way
Which is the Scavenger Hunt to find out more about the Mad King

Dates for when the different acts are happening are posted here: https://www.guildwars2.com/en/events/halloween-2012

I just wonder about this part:
The scholars of the Durmand Priory are concerned by odd energy fluctuations and eerie Halloween phenomena. Help them delve into the history and mystery of the Mad King in a series of all-new events.

I went to the Priory, but there’s just the usual NPC’s derping around. Anyone found anything further to that?

Thank you very much, was starting to go mad…