Magical Focus: Darkness?

So it looks like we will be starting up a new saga after a couple of years not playing, so this will be our first 5th edition game! Woo!

I'm thinking about making a magus who specializes in darkness spells, and am just wondering what people think about Magical Focus: Darkness. Would you rank it Major or Minor?

I am leaning towards minor, since it's seems to be just a single facet of Perdo Ignem. Can anyone suggest any applications of darkness that would be other arts?

Imaginem
Mentem
Corpus
Auram

Imaginem (sight sense) is an obvious choice. Stuff like fear of darness (mentem) or engulfing someone's mind in darkness (coma spells) would fit mentem well enough. Anything dealing with sight, emotions (fear, specially) and movement (teleport from shadow to shadow) can work well with this focus.

It is a cool focus for a not-so-good magus. Kudos for it. You can certainly find references in the bad guys of stories, like winter elves and goblins in caves.

Xavi

Just in case you're still wondering, it's now official in HoH: Societates page 28: