Inrau's death, as my name attests.
Any scene where "weak and foolish" Achamian lays waste with the Gnosis. Seriously, if he's just some low ranked shlub in the Mandate, imagine what his "betters" can do. But mostly it's the juxtaposition between his appearance/demeanor and what he's capable of.
The final scene of TTT. OK yeah, I'm kind of an Achamian fanboy. This scene sealed it for me tho. AC-DC be damned, Akka's got the biggest balls of them all.
Seswatha's dreams. I so want to know more about the first apocalypse era. The tidbits from atrocity tales only whet the hunger.
The few glimpses we get into the Chishaurim. Another mystery among the many that are barley touched upon.