Add

The Mystic Code sealing the Noble Phantasm Rhongomyniad, possessed by Gray.
Created by the Witch Morgan, she based the artificial personality within it on the knight with the least adoration for King Arthur from the Round Table. Thinking about the Atlas Contract Incident, that trick seemed more like a plot to “prevent the return of King Arthur” at that time. It was like a strange trick to say “I’ll help with your revival, but I don’t want it to succeed.”
Before being created, its true form was that of the Logos React Replica. Using the extreme calculative ability inherited from the Seven Superweapons of the Atlas Institute, it continues to seal Rhongomyniad within it. In its released form, it can of course take the shape of a scythe, but also that of a hammer, shield, hook spear, or even a boomerang. It is also able to use its immense calculative ability to display a portion of the power of Rhongomyniad itself. The appearance of the knight in “The Atlas Contract” occurred due to the same theoretical principle. Their personality was a result of a complex merger of that original knight’s and the present day Add’s, so strictly speaking it belonged to neither of them. That was likely why it was able to finally deploy the Pseudo Phantasm.
For Gray, Add was her only friend for a long time.
The name Add comes both from the word “addition” and from the tail end of the word “Rhongomyniad.”

Lord El-Melloi II Case Files material: Lord El-Melloi II Case Files Glossary