[talonthehand]

Originally Posted by Kelly Pedersen

If you don't think general magical theory is the right skill for magic portal operation, you can always create a new skill. That, in part, is what catch-all skills like Hobby, Professional, and Expert Skill are for. If you think operating a magic portal is average, it's Professional Skill (Portal operator), while if you think it should be hard, it's Expert Skill (Portal operator).

Hidden Lore (Portals) might be appropriate too.