Modding: Spells as secondary effects only?

[Starshine_Monarch]

What I'm asking here is if it's possible to mod certain spells to be unable to be researched normally.

Like say I wanted to mod in a new spell. However, I only want that spell as an added effect to a certain commander or whatever to represent some special, unique power of the commander.

I know I can always just give it some ridiculous path cost so nobody would even be able to use it, but I was thinking that I could put the spell somewhere where it can't be researched, like in Divine level 9 or something (assuming that even exists).