-PXG- said:
This is what I think. What else could it be.
Good question. Don't know enough about the lore myself and haven't read any of the extended fiction, but if I had to take a wild stab:
* Humans and more human-ish Locust shared the planet surface long before civilization was established. Humans drove some of their brethren into the caves and took the overworld as their own.
* Cave dwelling man went deeper and deeper underground and settled near immulsion reservoirs. Living their lives underground and in proximity to immulsion started to change them into the more beastial forms we now see in the game.
* Every once in a while a Locust would make their way to the surface, giving rise to boogeyman stories told by the peoples of Sera.
* Man discovers immulsion processing and the researchers eventually ran into the locust. Being liberal live-and-let-live types these researchers (including Adam and Myrah) sought to protect the locust and keep them out of the reach of Sera's growing military industrial complex (cue Avatar stuff here).
* Myrah decides to stay with the Locust and ends up caught in their conflict against the Lambent (as well as possibly the Cog). She desperately seeks Adam's help in this plight.
* Adam couldn't do it, and was still working for the Cog and helping mankind to kill one another in more efficient ways so Myrah grew distant. She united the locust and sought to return them to their rightful place on the surface, becoming their queen.
* Try as he might Adam couldn't develop a means to destroy the immulsion without destroying the Locust, and his relationship to Myrah gave him pause.
I'm probably way off, but given no other sources of information it's my best guess. Something along those lines. In terms of Myrah's radicalization, she may have seen or gotten caught up in Man's militant cleansing to secure their immulsion fields.
This still doesn't explain Adam's exact relationship with Myrah, or the locust relationship with immulsion, but I'd imagine the Locust used it as an energy source as did the humans. Its probably something deeper than that though.