-Kokonoe meets with Relius
-Relius offers to give Kokonoe a Murakumo Unit in exchange for help in making a Nox.
-Tager is created
-Relius' experiment with a cauldron creates a sphere that could spawn another Black Beast
-It's revealed that contained within each Nox is the Black Beast itself
-Kokonoe uses magic to purify the sphere, and thus Nu-13 is created.
-Nirvana kills Relius
-Some guy named Roy witnessed all of this happen, and if you take into consideration details from Carl's CS story, this would make him the third "Architect of Sin"
That's the most that I remember, so I hope this helps.
Anyways, now for a bit of stuff unrelated to what I just posted that I have discovered via CS2's Arcade Mode that could be useful to incite a little discussion, since this topic is pretty dry otherwise.
-Bang comments that Valkenhayn's outfit is similar to that of those worn in Ikaruga
-The reason Makoto wasn't in Calamity Trigger outside of flashbacks was because Hazama sent her to Ikaruga. There she discovered a bunch of failed Noel copies. Oh, and she also knew that Terumi had the BlazBlue, so props to her for being that smart without being an Observer.
-Makoto also comments on having seen Litchi before in the past upon beating her...
Nothing really of note came up during Platinum's Arcade Mode that wasn't already revealed, so yeah, that's all I got for now.