The Omega Weapon also known as "Light's Mirror" or "The Alpha Weapon" is rumored to be the second keyblade ever made and even rumored to be made by Omega. It was stolen by Vanitas and then utterly destroyed so Kingdom Hearts could never be opened again. It was somehow revived in GCIV as an obtainable weapon.
Gabe Chronicles Edit
Vanitas holds this blade.
Gabe Chronicles IV Edit
It can be bought as the best weapon with various gems most obtained by the Organization XIII.