What is the difference between New Gods and heroes who become gods?
There’s basically two things going on:
Heroes that became minor gods: These all fit into the Compromise, as none display “new” powers not already in place in the world. They interact with the God Time but are not truly part of it, and their powers are all devolutions of something already present in the world. Even Arkat (who is a marvel of the world by incarnating a succession of largely hostile deities) did not display something not already present. Even the Seven Mothers fall into this category. Nobody worries much about such deities.
New Greater Deities: These are “new” powers that did not exist in the God Time but have appeared in Time. The biggest of these is the Red Moon Goddess. There are no God Time stories of the Red Moon. And yet it is undeniable that She is a Greater Goddess, a universal cosmic power. Worse yet, she is associated with the Chaos Rune. She displays powers never seen before, claims to represent a Sixth Element and often manages to prove that 1+1 =3. She is still unsettling after four centuries!
Nysalor is something else. He was born in Time as a result of a the God Project of the mortals, but his empire was accompanied by Chaos. Not sure if he was a violation of the Cosmic Compromise, an attempt by Wakboth to return as Gbaji, but whatever it was, he was bad news. He’s dead though, torn into a thousand pieces. We would entirely forget about him, but for his close connections to the Red Moon Goddess.
Note that some fans have conflated the appearance of a new greater god (the Red Goddess) with worship of a hero who becomes a minor deity is IMO an attempt to create confusion. Having a bunch of new lesser gods who fit into patterns that exist already in the spider’s web is nothing new. Besides these lesser gods mainly deal with things that have occurred within Time – so for example, Dormal lets us get around the Closing (a Second Age magical curse on the seas); Sartar blesses the dynastic rulers of the kingdom that bears his name; and Arkat fought a new god that appeared within Time.
The Red Goddess is something altogether different, and everyone in Glorantha knew it. The scale alone was unprecedented. And that she appeared in the Heavens was even more startling – a new celestial being larger and brighter than anything except the Sun! And associated with Chaos! And She’s managed to beat everything that has been thrown at her – Yelm, barbarians, a great world-conquering nomad empire!
There’s just no real comparison here.
Also misguided because most Lunars are perfectly willing to boast that their Red Goddess is something new and unique. Of course She is a new element and/or condition in the cosmos. That’s how awesome She is! To compare her to some figure from barbarian legends is just insulting!