For understanding the Malkioni approach to sorcery, runes, and gods, the Xeotam Dialogues, written by Greg back in the 1970s, is absolutely invaluable. Here’s a link to an abridged version of it:
Greetings Glorantha-philes! Today’s posting is a rare treat – a fragment of the Xeotam Dialogues, that proved so popular amongst the Western sorcerers in the later Third Age. The date of the original Dialogues are believed to be circa 1480, although this particular copy is dated from 1618.