I WONDERED about that too! o.o
Maybe it is Metal Sonic o.o

See my reply below =P

Apparently, according the the script I found on the net somewhere (whether it was true or not I have no idea) it was supposed to be that sorcerer guy that appeared during that series, the one Robotnik feared.

Snivly allied with him...somehow Robotnik survived...Robotnik became socerer guy's pet and kicked Snivley out...snivley joined the freedom fighters and all manner of stuff happened.

Ah, Ixis Naugus there we go.

http://en.wikipedia.org/wiki/Sonic_.....)#Plot_summary

you Really not seen the seasons then to think that

1 Nexus is Stuck in the Void thought he was able to exit it thanks to Sonic but he can not stay cause he be turn into Crystal and die
2 Nexus's eyes do not Look like that what was behind the 5 last hears headed one
3 the only other person it could be is Shadow but he was not made around that time

Erm...
The WRITER said that's who it was. You know, the person who CREATED the series. Read the wiki.

And his name was Naugus, not Nexus.

we have a winner

then you should tell this friends of mind that then cause said it was Metal also them EYE! are like Sonic's and Nexus does not have EYES like that and stop commenting

I'll take the word of the guy who wrote the story over some friends of yours who I've never met, thanks.