So, honerva doesn't exist in this AU, Keith basicly is in her place and it diverts for canon from there.
Altean Keith is an alchemist who traveled to Daizabaal to research the fluctuation of energy emitting from the planet, this is before the comet comes and the rift and build Voltron.
As basicly the royal alchemist and cousin of the altean king, Keith is big news, but he doesn't care much for the attention and responsibilities of royalty, he is all about his research.
Moving to Daizabaal means he has to consult with Zarkon alot, over time they grow close, Keith is oblivious at first cause he is focused on his research and galra courting habits aren't common knowledge to alteans.
Basicly it's Alfor who informs Keith that Zarkons strange behaviour is him trying to court Keith, Keith doesn't immediately become a blushing mess because he never considered romancing when he left altea, so instead of being awkward Keith is just more observent of Zarkon after learning about the courting.
Eventually Keith and Zarkon become mutually sappy and find towards each other and they become official.
It's around this the the comet arrives and Alfor gets obsessed with it much to Keith's annoyance, he may not be particularly fond of his cousin but he isn't used to his cousin outright ignoring him to focus on the comet.
It's fine though cause Keith focuses on the rift and quintessence to Zarkons annoyance, it puts a strain on their relationship for a while til the lions are finished and Zarkon becoems busy as well.
After awhile they decide to take time off their obsessions to have a wedding and share their time together, to prove to each other they haven't forgotten each other.
During that time Alfor looks into the research of the rift and realizes it is more dangerous then he ever considered.
Alfor interrupts Zarkeith time and gets into an argument with Zarkon.
Keith realizes his downtime with Zarkon is over cause Alfor is a jerk and goes back to research.
The strain on the alliance becomes noticable from the other members of Voltron and people start taking sides.
It all really blows up when a lab accident caused by tampering ends Keith's life, Zarkon banishes Alfor from Daizabaal.
Alfor and the other paladins retreat to let Zarkon mourn, but that doesn't last long.
Zarkon goes into the rift with Keith making it visably unstable and Voltron takes this opportunity to go behind Zarkons back and attempt to destroy the rift by targeting Daizabaal.
It doesn't completely work as planned, Zarkon leaves the rift with Keith, who is now white haired and sharp markings and pale skin and not dead, but not awake.
The rift closes upon their exit, in the ensuing backlash Alfor sends the lions and the castle away and holds the galra army at bay long enough for them to escape and then the altean army falls and altea is destroyed.
-time skip to when Keith wakes-
Keith has lost all his memories as his price for life, and has no idea who he is.
Zarkon is there though to tell him, though Zarkon is more intense and obsessed and angry now different then he was before.
Keith while he doesn't know Zarkon like he did still feels a attachment towards him, drawn to him, so he stays.
He starts new research, for the betterment of the galra, gathers quintessence sensitive galra as followers dubbing them druids, becoming himself their high priest.
-time skip to Keith descovering shiro-
Keith isn't heartless, but he isn't always merciful, everything he knows is what he has experienced with the galra after his awakening and what Zarkon taught him.
The empire is all he knows and he uses all his means to empower and protect it.
Arena participants aren't just for entertainment, they are the biggest source for experimentation subjects, tests are made on the fighters before deemed viable enough to grant to the armies strongest. (Like how sendaks arm is an upgrade from Shiros, Shiro was a prototype test)
The druids only take interest in the strongest of the fighters, the champions, the winners.
Keith's current focus is a gladiator named myzax, he isn't quite satisfied with myzax's weaponry completely sending him into battle over and over to find flaws to improve.
He is watching the battle when Shiro takes myzax down in his first battle.
Keith has myzax dragged back to his lab in frustration, myzax his repeated champion lost to a new face.
After thoroughly punishing myzax and dismantling his enhancments for thorough reviewing, Keith turns his focus to shiro.
He watches battle after battle of Shiros victories, he gets curious, orders druids to drug Shiros food.
Sometimes with boosters, sometimes with weakeners.
Shiros wins only increase and so does Keith's interest, Zarkon notices coming to watch the matches sometimes to see what has taken Keith's attention this time.
In a particularly brutal confrontation Shiro injures his arm as a tactic to get an upper hand, Keith notices.
Keith thinks 'if his arm were stronger he could have taken the upper hand without sacrifice'
Keith orders Shiro to his lab.
Keith along with ulaz and two druids have the lab prepped for shiro when he is delivered.
Shaken and still running on adrenaline from his fight Shiro is confused and apprehensive about being brought somewhere other then his cell.
For now they only take in his vitals and conditionings.
But over time Keith continues taking Shiro after fights to test his endurance and constitution, marveling at his strength and adaptability, the latter of which surpasses galras abilities to adapt.
Just when Shiro gets used to the testing and less apprehensive, Keith decides to take his arm, which has long since healed.
Shiro is of course traumatized.
Shiro is left in the lab with Ulaz tho when Keith is called back by Zarkon who has located the blue lion, Keith is not happy about being interupted but humors Zarkon regardless.
Keith having forgotten the prerift trip, has forgotten about why Voltron is such a big deal and believes they can better the empire without it, but keeps that to himself.
Meanwhile ulaz frees Shiro and sends him to earth.
Keith will not be happy to find out about that, seeing as he decided Shiro is the perfect subject to better the advancements of the empire greatly.
With Shiro gone, Keith has nothing better to do then assist Zarkon in retrieving Voltron and guiding his druids, the former is much to his dismay.
When the information from sendak comes back that the black paladin is Shiro, Keith takes confronting Voltron alot more seriously and starts by sending myzax at Shiro.
Keith's attention is soon completely taken by Voltron, every win just makes Keith that more obsessed with Shiro, seeing Voltrons strength as Shiros.
So basically Zarkon wants Voltron, but Keith wants Shiro and Zarkon low-key wants to kill Shiro for flying the black lion and Keith is willing to over throw Zarkon to obtain Shiro.
Keith is an obessive mad scientist druid priest, this is not Sheith.
-will return to this one-