This reminds me of an old idea I had for a dnd character once and I can probably adapt it to this

A warforged built by a cultist to server his god. He was found just before the machine was officially set loose upon the world, and the robot was put in a coffin or some other hidden compartment, and found way after. This machine was "coded" for lack of a better term to have forbidden magic up its sleeve, but doesnt really know how or why. 

All he knows is that he has a weird innate ability to use these forms of magic, but for some reason he can't use any others. Likely because hes a literal robot and shouldnt have magic abilities anyway.

How viable is something like that?