A few years before the start of my book series, a galactic plague of a disease called BigPox is going to spread through the galaxy and inflict mass casualties, in addition to setting many of the elements of the story into motion. Here are the events that are required to happen, along with a map of the south galaxy (the dots are star systems, the dotted lines are trade routes, and the blue line is irrelevant here):
So here's my question: how can I imply that this plague scenario, happened before my first chapter, has made a dictator from Caput Tatiium develop dreams of galactic conquest? In other words, how do I imply that this plague happened without wasting time setting up stuff that doesn't really have much to do with the plot later on?
I want the plague to be relevant to the setting, and the main cause of some events, but nowhere near the "focus" of the entire story.
Some additional information about the effects of the plauge on my galaxy:
-The Rinascitan Monsquistadors spread the disease to Aztlan, causing the deaths of 40% of its population, including the mother of Nate, one of the main characters. (NOTE: THE "NEW AZTLAN" ON THE MAP IS AZTLAN; IT GETS A NAME CHANGE LATER ON IN THE SERIES).
-Vigam is hit particularly hard, with the Lunar Cliffs area losing its rulers and 80% of its population. Vigam in general loses 70% of its population.
-The plague misses Aurea completely.
-Planet Squid loses ~2/3 of its population
-Ishga medicine prevents Ishgabangaloodoo from being hit too hard, but its monarch is too greedy and paranoid to share the cure with anyone else. Ishgabangaloodoo loses only 5-10% of its population as a result.
-Awal Kabab is hit hard, losing 60% of its population
-Caput Tatiium is so far removed from the rest of the galaxy that there are only 5 total reported deaths.
-Arturia is hit hard, particularly the city of Caerbannog, which loses 66% of its population. Weasel's father falls ill and dies. Arturia in general loses half its population.
-Everywhere else loses anywhere from 15-20% of its population
-Symptoms are a combination of smallpox, ebola, and bubonic plague
-There is a 100% mortality rate without treatment, but with treatment it is closer to 12%.
-The Ishgas are the only civilization technologically capable enough to have a working treatment (every other planet has Renaissance-era technology or worse, using magic-powered spaceships instead of electric-powered ones like the Ishgas).
-Although primitive, most of the less advanced planets do know enough about disease not to pull any of that leeching or bloodletting nonsense and instead attempt to quarantine the sick
-Melzac is unaffected because it is no longer inhabited
-Although humans are rare in this universe, every sentient species has physiology superficially similar to that of humans, allowing the disease to wipe out basically everyone at the same rate
-The plague lasts 10 years
Some things to know about this conqueror:
-His name is Tate
-He and his parents are humans with a mutation that gives them absurd magical ability and the ability to transform into 2 more powerful forms
-He lost an eye as a child in the explosion that killed his parents, forcing him to rule Caput Tatiium from the time he was seven years old
-He rules over all of Caput Tatiium with an iron fist, extracting outrageous tributes from its twenty or so tribes
-He views basically everyone besides himself as inferiors
-In order to earn his trust, you must earn his respect, and in order to earn his respect, you must be a magical prodigy
-He has no empathy towards anyone (he is a sociopath)
-He will do anything, regardless of how "low" or "dishonorable" it may be, to get one up on anyone who gets in his way
-He is extremely smug
-He is extremely witty, vulgar, and sarcastic
-He is a heroin addict, but his mutation shields him from most of the drug's negative effects
-He views himself as "above" the concept of good and evil
-He doesn't like routine
-He is very nihilistic
-He is one of the most intelligent people in the galaxy, pulling off gambits that baffle his own generals
-Unlike most sociopaths, however, he can feel the emotion of love (but this is very rare and only happens with one person later on in the series. He attempts suicide via intentional heroin overdose after this though).
-He suffers from intense depression and self-hatred, but hides it
-He is extremely spiteful of anyone who criticizes him or gets in his way
-He is apathetic and lazy about anything that does not directly involve him or the needs of his empire
-Feels very ambivalently about death (he seems like he has a fear of death at other times, but seems to actively seek it at others)
-Has no problems committing multiple genocides
-He has lived his entire life with the belief that nobody would ever come close to matching his magical ability
-He says his moral code is to never kill without reason, but he counts "I was bored" as a reason
-He often over-indulges himself at parties or other social events
-He is a hypocrite
-His political beliefs would be considered Communist in our universe
-He uses manipulation and promise of reward to gain allies