The bit about ACT 2 i totally agree, there is some weird ass areas on that map that are never explained at all, massive monstrosities that are just sitting around waiting to kill you with slim to no plot points explaining why.
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I think they are related to the "Three altars" quest that you receive from the undead scarecrow and the story of the sorcerer that made them, It´s the one that sends you mental messages when you are exploring. As every act is an "open world" of sorts there are high chances that you killed a few of them before even talking to the scarecrow, or you killed the scarecrow too, depending on what direction you explore after leaving Driftwood.
