About the scope of the focus, I thought a little.
A mMF is narrower than a Technique + Form.
A MMF is narrower than a art.
Given the whole of Vim, I figure "Supernatural Beings" would thus be a proper MMF.
Limiting this to Magical Beings cuts this by 4. Would this be OK for a minor focus? I'd probably say yes, but YMMV.
Now, "Beasts of Legend".
If we start with Magical beings but add another limit (like "Magical Animals"), this further cuts the focus, making it even smaller.
But, as I noted above, there is no realm limit to the focus. It acts upon all realms.
So, if "Supernatural Beings" is a MMF, how can an "accros the realms" focus in "Beasts of Legends" be minor?
Well, I'd define it as "Corporeal supernatural creatures that do not look like a mundane animal nor are human in form".
So exit spirits, exit white stags, exit giants too, but enter dragons, griffins, 3-headed dogs, that sort of things, from any Realm.
Hope this was useful / of some interest to someone 