Black Legion weren’t originally on the list for faction of Grim Dawn. They are like the Rovers in that you have to join them to advance the major parts of the story.
Once you are done with the Quests in Act 3 part 2 you will then eventually find the two other factions where you’ll be able to join one of the two. These two factions will be seen more of in Act 3 part 3 in B26.
have you done all the quests that can be completed so far?
If you kill the The amalgamation (quest) and return to Homestead you eventually speak to Ulgrim who says that you have to choose between the 2 factions
they can be found in the main building in Homestead
Thank you for letting me know. I was planning to do the other missions first anyway before responding to the Black Legion.
I hope in the next Faction upgrade they make that a bit clearer in game. I believe the other two big factions should appear a bit earlier and make it clearer for the player that there are options to choose before a player makes a choice just by who turns up first.
The two factions show up at the same time and both have dialogue options in telling who they are, what they represent and why they disagree with the other faction.