I watched all the credits of Kingdom hearts birth by sleep,and when we see Olimpus Coliseun,it shows Phill training Hersules and Zack cornered,then Zack see a black feather,everything turns black,and then we see the black feather again.I think it should have something to do with Sephiroth or another chracter that is from FFVII Crisis Core.

Any ideas?

I agree It was Genesis. Sephy's wing in KH are dark navy blue.

I always kind of thought it was Sephiroth abducting Zack, but I don't know for sure.

Well, I wouldn't say he's "dead." Aerith is supposed to be dead too, right? But she's still in the KH series. I imagine/hope we'll see Zack again. I doubt they would include him in one game and then be done with him...

maybe a kh3 polt point?

maybe a kh3 polt point?

This is a very possible point for it. 

I think this all might actually be settled in the inevitable Cloud appearance in KH3...

 

I believe it's strongly suggested that in this universe, Sephiroth went on to kill Zack, and that this makes Cloud who he is in KH1 and 2... Cloud persuing Sephy to take revenge for Zacks murder...

 

The fact that Cloud first made his appearance in Olympus Colliseum, just like Zack, was used by Hades, just like Zack... that you fight Sephiroth the first time in OC, and that Sephys feather landed in front of Zack in the BBS credits...

 

Theres just a lot to do with those three people and that place that can't be ignored.

I think this all might actually be settled in the inevitable Cloud appearance in KH3...I believe it's strongly suggested that in this universe, Sephiroth went on to kill Zack, and that this makes Cloud who he is in KH1 and 2... Cloud persuing Sephy to take revenge for Zacks murder...The fact that Cloud first made his appearance in Olympus Colliseum, just like Zack, was used by Hades, just like Zack... that you fight Sephiroth the first time in OC, and that Sephys feather landed in front of Zack in the BBS credits...Theres just a lot to do with those three people and that place that can't be ignored.

Good theory; I'd never put all the pieces together like that before.  In a sense, I guess they really were enacting FF7 all over again--in a KH sort of way.  Still, I wonder if Zack's really dead, though...  A feather isn't a whole lot to go by, but it would make sense.

Since Sephiroth resides in Olympus Coliseum in KH1, it has to be him without a doubt. 

I wouldn't be surprised if Sephiroth came and attacked, then Herc tries to help Zack, but failed and Zack was killed. Or taken away into a bat cave, where he's being enslaved by Sephiroth.

I think I'd prefer the second option more, but I also can't deny the first one.

Yes it is Sephiroth. That's just it though, it is unknown what happened to Zack. I think KH3 will answer all questions to every mystery of the series we have learned.