On the topic of Durge / Ketheric / Durgetash and how it potentially echoes the lore of the Dead Three...
Back in the mortal adventuring days of the Dark Three, it was originally just two power hungry humans with a common enemy who'd gained respect for one another's capacity for ruthless violence and paired up - not so different from Durge and Gortash.
The duo was comprised of Bane of the Ancients (a former battle slave to a primordial evil from Abeir) and Arabhal (a chief assassin and spymaster from ancient Netheril).
Long before Myrkul joined the party, Bane and Bhaal adventured together seeking power for themselves, plotting to slay Bane's former master and take divinity from Jergal (Bhaal's patron deity). Sort of like how Durge and Gortash were allies before Ketheric joined the cabal. I can see Durgetash plotting to ascend together.
See where I'm going with this?
Anyway, Jergal thought they were neat. He encouraged their antics by blessing them with terrible nightmares and leading them to powerful weapons - most notably, leading them to Myrkul (a crowned price and powerful necromancer). It was Myrkul who finally managed to gain the three access to Jergal's domain, and Jergal really wanted to retire.
I suspect Bane and Bhaal remembered how critical Myrkul had been to their initial ascension, and that was why Ketheric Thorm was eventually looped into their new alliance.
Despite Bhaal and Bane's long history together, something funny happened following their ascension. Suddenly Myrkul and Bhaal have way more in common. Their portfolios make them natural allies. In the Avatars novels, Myrkul actually grieves the death of Bhaal, noting that one could hardly exist without the other, and states that 'amongst all the gods, they were perhaps the closest'.
Which means... Bane isn't Bhaal's favorite anymore. In fact, Bhaal can seriously fuck him up. While Myrkul truly appreciates the lord of death and murder for feeding his kingdom, Bane has as much to fear from Bhaal as to gain from him. (technically Bhaal claims he could starve Myrkul's kingdom, but since he really enjoys killing and hates the living world, Myrkul's kingdom is probably like a vacation home he'd prefer not to burn down.)
What we see after a thousand years or so of this is Bane antagonizing Bhaal every chance he gets, and profiting off every one of his failures. Bhaal picks a fight with the Moonshaes and gets exiled from Toril? Bane sees free real estate and conquers the wreckage. Assassins fail to kill the mortal Midnight (Mystra) and retrieve the tablet of fate during the ToT? Sacrifice them all in a massive death ritual to fuel Bane's new avatar! Bhaal is dead and his remaining loyalists team up with Bane's kid to bully Cyric, who usurped them both? Return in a pillar of fire and annex them into the church of Bane! Sucks to suck, your worshippers are mine now. Again.
I can see a BG3 prologue where Gortash and Durge are super best friends right up until Ketheric Thorm joins the party. I won't get into all the reasons why Ketheric's and Durge's personal issues make them ripe for toxic bonding, but suffice to say that Gortash soon gets jealous of the undead immortal stealing his Bhaalspawn's attention and (whether unwittingly or out of spite) leads Durge down the path to ruin (shooting himself in the foot in the process).
Meanwhile, Bhaal (who has been raging at Bane for stealing his stuff for the last century or two) is now raging at Bane and Myrkul for fighting over that stuff until it physically and mentally snaps and becomes a hero.
Now it's ruined and I have to settle for Orin. Fuck you both.
Darth Revan: Never ever talk to your kid. Do everything to make sure they are safe but NEVER EVER interact with them... Oh and keep holos of them.
Darth Vader: Maiming your kid is okay-parenting if you say "work at my shitty job with me" later.
Darth Bane: Raising a kid in isolation and with nothing but a few old tents as shelters is adequate.
Darth Sidious: So I got this horned kid gifted to me and I kind of never really cared. But the little one turned out quiet capable actually so I had to try kill him. But that was a strongly communicated lesson and I would do that again.
The internet eventually made major label distribution irrelevant as a necessity for gaining wide exposure, but in 1994 a big record contract was still very much a requirement if a band wanted to break out of their local scene, and not being signed to Warner or Sony, or even Roadrunner, was likely why Lord Bane didn’t last beyond Age of Elegance. Then again, they broke up almost immediately after their one album came out, so maybe they had their own reasons for not sticking it out. In any event, “Born to Die” highlighted Lord Bane’s version of progressive metal, mixing a heavy dose of Images and Words-era Dream Theater with prime Crimson Glory and leaning towards the more metallic side of both. This was prog metal that didn’t really emphasize prog over metal or vice versa, and was all the more enjoyable for it. Given that Dream Theater was already semi-successful by that point, Lord Bane might’ve had a shot at riding their coattails, though apparently they had other things in mind.
Durgetash secret code idea: Bane and Bhaal both limit the other god's visibility over their Chosen, leading to each of them only getting to spy on 'their' half of the conversations. Each Chosen gets to look good to their respective deity, who has no idea what actually took place.
I find it funny that the original Dead Three were a classic party of fighter (Bane), rogue (Bhaal), and mage (Myrkul).
The Chosen in BG3 switched it all up. Now Bane plays rogue, Bhaal plays spellcaster (assuming default/sorcerer Durge) and Myrkul is the tank.
I wonder if they criticized each other's choice of Chosen or just fought over who got what role in the party.