Uhh... I'll give you a summary on here, just to make things easier. 8D;
I think all that's really happened is Alt, Ei, Derrick, and Rena fought through a crowd of corpses and went into a clocktower. Ei and Rena found the keyhole, which was sealed and crazy things started to happen because of it. Aoi was fighting Sleif, until he jumped off to the clocktower to get to the darkness that was beginning to appear there. At the clocktower, Castex appeared and talked, while a hound appeared out of Rena's keyblade. Annnnnd Ei revealed a door through the keyhole.
Kinda confusing, so I suggest reading the last few posts to get a general idea of what's going on. ^^; From KKL's post to the latest would be best, I guess! Hope that helps!