In KH2 FM, Xemnas (i think?) types in a password in the computer. This password is "another" which is an anagram of Xehanort without the X. The passage it opens leads down to where aqua's armor and keyblade are being kept and he called it friend. It's known that Xemnas was searching for the room of sleep but never found it. So, the password another could be referring to Ven, as in another friend. If he never found it, maybe he figured if he was there when the change from LoD to CO happened, he would know where it was. So he either sent something else back or went back himself to find out where Ven is. As to WHO it is..it's possible he could've combined the data replicas into one and sent it back as it does have powers from each member. Whirlwind to the void, which knocks out your commands, was Marluxia's for example. The clones could be from Zexion. The time from Luxord. The fire tornadoes from Axel. And the...thing where he like distorts himself and appears somewhere else..thing..from Xigbar. Which would also explain why the data replicas exist. Not too sure on the who but the why he's there i think is somewhat probable. What does everyone else think?