As stated in a Facebook post by WEBZEN, a Monster Invasion will be taking place on Aibatt on Friday, 11/15/2019.

The GM-hosted ‘dreadful invasion’ will be starting at 5 p.m. (UTC).

Further information is supposed to be available in a post on the official forums. At the time of writing this Newsticker entry, no further information can (unsurprisingly) be found there.

Update (11/14/2019): A post on the official forums can now be found which states the location of the Invasion and vaguely hints at possible monster spawns.