Unlockable: Model OX
On Normal you must defeat Omega in N-1, then go past the door which says "I need something to open this door. The Game Pack Megaman Zero 4 is needed" and enter the next one. Youll get Mysterious Rock.
Then, after you defeat Serpents final form, you should have "COMPLETE" over your save file. Now go talk to Fluub, and hell say its Model OX.
