Where did they come from, where did they go? Is their primarch

https://en.wikipedia.org/wiki/Battle_of_the_Teutoburg_Forest

>>50882546
Interesting theory if they had used the same numbers.

What would cause the greatest defeat for Spess Muhreens? Losing to the Tau?

>Is their primarch Cotton-Eye Joe?
Probably not? They were excommunicated before the Horus Heresy, right?
Which means they weren't doing Chaos shit. The Primarches didn't know about Chaos yet.
Couldn't know about Chaos -> Couldn't be a Nurgle follower -> Couldn't be Cotton-Eye Joe

Big question is... What have the II and the XI done to be expunged? what could be worse than Horus Betrayal!

>>50883929
I'm pretty sure book 3 implies Chaos (potentially minus the Dark Gods' direct involvement) might have been involved with one of the missing Legions' downfall. From what I gather, one downfall is attributed to some sort of shaming failure in their development or shortly after their formal introduction, the other being explicit betrayal.

>>50884029

Possibly openly working with xenos could be one answer. There were a whole lot of horrible xenos out there and to make yourself a pawn of one would be pretty damning.

Xenos pawns/allies and AI Tech Heresy are my guesses.

>>50882581
Something a little more "NOMNOMNOM" is my theory.

They became the Angry Marines. The primarch is Rachnus Rageus. For fuck sake, do you not know your /tg/ history?

Mindwiped Thunder Warriors who started having flashbacks