If you don't like Greg's answer for your varying Glorantha, here's a few
other ideas:
- The Court was the first interaction between the 3 or 4 worlds, and
it was cooperative. You could map each world to a different type of rune,
if you want, or mix them. (E.g., perhaps the spirit world supplied form
runes. Or maybe they supplied darkness, fertility, and beast runes.)
- It's a god learner amalgamation of culture-specific groups that were
really separate.
- They were the giants in the pre-creation war between the giants and
the dragons.
- There really was a Gloranthan court. They were a side effect of the
worlds coming together. They were like common magic, native to the world.
Chris