There is no Red Earth subcult of Ernalda. In Tarsh, about 10% of the adult population are initiates of Hon-eel. About 25% are initiates of Ernalda. They are separate cults.
Hon-eel tried to become accepted as a Grain Goddess – which would make her associated with Ernalda. During her lifetime, Hon-eel was able to pull this when she was physically present, but when the Earth priestesses discovered that Pyjeemsab was dead, the Shaker Priestesses (and likely the Feathered Horse Queen) put an end to that. Hon-eel’s initiates are not able to enter Ernalda’s rites as an associate. It would seem that is a dead end – proof of Hon-eel’s remarkable power but she was not able to pass that on to her cult.
And so Hon-eel’s cult is a strange one. A Grain Goddess associated with Dendara, but not with Ernalda. That path might be able to opened again, but the Tarshite cults of Ernalda, Maran Gor, and Babeester Gor are hostile towards Hon-eel, so good luck trying!
For the Ernalda/Maran Gor cults, Hon-eel is a betrayal and a murderess. She secretly killed her sacred husband Pyjeemsab in order to plant her son on the throne and secure the south.
Now I think Hon-eel knew that was likely to be the outcome of killing Pyjeemsab but figured she had gotten what she wanted out this – a Lunar foothold in Tarsh. She could leave that in the care of others and she could go on to focus on more pressing matters in the Lunar Heartlands. Hon-eel established several dynasties, and Tarsh was hardly the most significant.
As an aside Hon-eel had performed this sort of quest previously – remember, that Hon-eel also proved herself the mistress of Yelm to the Pure Horse People, and bore the Sun God children. That managed to keep the peace with the Pure Horse People for a generation, but in the end the Pentans rejected Hon-eel and killed her during the Nights of Horrors. And so even though Hon-eel is associated with Dendara, I strongly doubt her cult has made any progress with the Pentans through that opening.
Hon-eel’s goal was not to end up as an associate cult of Ernalda – her goal was to secure the southern flanks of the Lunar Empire. In that she was very successful.
To build that solid stronghold in Dragon Pass meant she needed her son to rule (as Hon-eel sure as hell wasn’t planning on sticking around in Dragon Pass). To do that meant killing Pyjeemsab at the first opportunity.
Doing otherwise was far riskier, far more costly, and not really relevant to her goals.
She tried to be accepted as a Grain Goddess, which worked until she murdered King Pyjeemsab. But that was for her a price worth paying to get a permanent stronghold in Tarsh.
And this leads me to point out a common mistake I see in many forum discussions – people looking through the wrong end of the telescope. Hon-eel’s activities in Tarsh might be incredibly important to Tarsh, but they were not particularly that important for Hon-eel, just one of many things she did.
And the Hon-eel cult in Tarsh is very important to Tarsh, but Tarsh makes up maybe 1/8th of her cult.
Greg regularly hinted that Hon-eel’s bloodthirsty pragmatism bothered many Lunars. But she was so damn successful. Her cult and her family has no end of enemies within the Lunar Empire though. But again, they have been so damn successful.
Hon-eel got what she wanted. She needed to be accepted by the Ernalda priestesses in order to get there, but was happy to discard that in order for her son to be acclaimed king. Consider it she managed to get a card that let her do something even more impressive, but needed to discard that card once played.
Her goal was to secure the Lunar Provinces, presumably by founding a big colony there that could be an anchor. To do that, she needed an invite – the Lunar Empire was not militarily strong enough to do that by force (remember this is only 30 years after the end of Sheng Seleris and the nomads are still an existential threat).
So she announced herself as a Grain Goddess, waltzed into the Ernalda inner rituals, and was accepted there. She married the Tarshite king, who was a sacred figure, the brother/husband of the Earth Goddess, and gave birth to a son. But she needed to get rid of her husband in order to found that colony, so killed him/had him killed whatever. That lost her the support of the Ernalda cult, but a small price to pay. She acclaimed her son as king, got others to recognize him, and then settled thousands of Lunar Heartlanders in Tarsh with the royal approval. Sure most people objected to this, but there was no organised opposition. And before anyone really had any idea what was going on, it was a fait accompli! The Empire had its stronghold, the Lunar Provinces were secured, and Hon-eel could go back to Glamour to do more amazing things.
That is why she is a goddess.