Two-level randoms?

[llamabeast]

I could have sworn that I used to know how to give two-level randoms to units. I seem to remember it was restricted so you could only give either "elements" or "sorcery" (i.e. the random gives two levels in one of nature, astral, death or blood).

However, I now have no idea whatever how to do this, and am beginning to wonder if I imagined the whole thing. Does anyone have any ideas? I want a 2-level sorcery random. At present I'm using an ordinary sorcery random plus #magicboost 1, but that is super-clumsy and will cause weirdness if the unit ever gets empowered.