First of all, what is a Monthly Adventurer Campaign you may be asking? This is the term we dubbed for SE to classify the random monthly campaigns we have received since the release of Seekers of Adoulin. It all started with the very first one, a double EXP campaign which only lasted a couple of days.
As for the reason of the creation of this thread, now have a BG Wiki page that lists every Monthly Adventurer Campaign, as well as an explanation of what each of them does. Never fear, as each section is included on the relevant BG page. Here is the Vagary page and location of the campaign info as an example. Because of this, you should not have to refer to this long page of text unless you want to see them as a whole. If you do though, there is a mile long table of contents on the right for your convenience.
I am planning on adding redirects to this page if you search for a campaign name. Also, we might list all of the dates that each campaign has taken place. That will only be done if we get bored enough to research and list them, or if there is enough community demand.
Lastly, sorry this was not around last year during the "Let's Go! Vanadiel Day!" events. It could have helped at least one player for 24 hours.