Spoilerful discussion below. If you haven’t read up through LN4, then proceed at your own risk (I will not discuss LN5 or mobile game only content).
Trailer discussion
0:22 Is is just me or does this ghoul appear suspiciously similar to Skel. I just thought it was funny.
0:33 We see Aurora in a casual setting wearing what seems like a lab coat? As far as I know this was not in the LNs. The only Aurora we should be getting is when she possesses Claire’s body in the fight with the Blood Queen. Perhaps this is an anime original scene? Also, it could be something to help set up LN5 content post-Vampire arc. I am betting that they animate Claire/Aurora discussions similar to Smeagol/Gollum discussions and just change POV and character model.
0:39 Brief glimpse of Victoria/559 (confirming LN4 content in this season). The LN doesn’t really go into her backstory, but the mobile game’s story provides some more background on her.
0:51 More confirmation of LN4 as we see Rose in her wedding dress.
0:53 Delta blowing up a train car as well as first appearance of John Smith. I am guessing that the anime is going to reskin the horse-drawn carriages from the LN to be train carriages.
0:55 We see Elisabeth/Blood Queen doing her thing. I hope they give this fight the anime-style glow-up that they gave the finale of Season 2. In the LN, it felt a bit underwhelming considering all the combatants involved.
1:06 Best girl and drill-sergeant of my heart, Lambda (fight me!) makes a brief appearance. Not too much backstory on her in any format yet. The most probably appears in the mobile game, but still it is pretty sparse.
1:07 We see Victoria and Zeta together. Not sure what could be going on here as Zeta does not appear in these arcs at all. Perhaps some anime foreshadowing of LN5 content.
1:08 Alpha fighting John Smith, again on a train instead of by a carriage, aligning with the previous Delta fight.
1:17 Not sure who this girl is, but my guess is a young Yukime from a flashback when she is recounting her history with Gettan based on the hair/eyes.
1:26 This object looks similar to the Eye of Avarice from Season 1. Not sure what it is doing here…perhaps we might see some anime-only Sherry content?
1:39 I believe this is the first we have seen the cover for LN6. Looks like it features a clown(?) and a girl the might be Victoria. All of the other covers have had Cid in one getup or another plus one or more girls. So, I am guessing that the clown figure might be another of Cid’s alter-egos.
Spoilerful discussion below. If you haven’t read up through LN4, then proceed at your own risk (I will not discuss LN5 or mobile game only content).
Trailer discussion