There is a LOT to talk about with these, and they're very interesting. I'll do a quick bullet-pointed list for people who don't have the time to read right now, but want to get the basics. Although you should read them, they're good.
"Where Icathia Once Stood"
-Icathia was once conquered by Shurima, before they rebelled, which is when the story takes place.
-The narrator is part of the Kohari, an elite group of Icathian warriors.
-There is a Kohari by the name of Saijax who wields a large polearm, is wary of the Void, survives the story, is a master of combat, and has an apparent love for eggs. That all sounds...a little familiar.
-The Kohari attempt to fight off an invading Shuriman army, including some Ascended, by having their priests unleash a mysterious power. It's the Void. The land is covered in Void Goop, the corpses are mutilated and changed, and the city is warped by the Void. The narrator begins to slowly lose his mind as the story ends.
Kassadin
- Kassadin is not his real name. It's the Shuriman phrase "Kas sai a dyn" ("whom does the desert know?") poorly pronounced, and it stuck when said constantly by people looking for him.
-Kassadin is a skilled explorer and archeologist/treasure hunter kind of guy.
-One day, he returns home to find his village destroyed, and his wife and daughter nowhere to be found. This is Void doing. He learns of a "Prophet" who may be trying to pull the Void back into Shurima.
-He uses his connections from work to craft his signature armor, using talents from Zaun and Ionia, likely among others.
-His sword is a Shuriman weapon called the "Nether Blade of Horok".
-He sets out for Icathia, ready to kill the Prophet, or die. Or both.
Malzahar
- Malzahar is a Shuriman orphan who grew up as a street fortune teller. He got famous for being very, very good at it, but could never see his own destiny.
-Sick of watching the gaps in wealth and despair that society brings, Malzahar leaves his hometown of Amakra and starts to roam the wastes.
-While alone, his visions get worse. He sees how terrible people can be, and what awful things might occur.
-He stumbles into the ruins of Icathia, and is touched by the Void. It...changes him.
-Malzahar now sees an end to the suffering: FEED THE WORLD TO THE VOID. He sees himself as a savior.
-He accumulates followers with his newfound powers, convincing them to make sacrifices and offerings to the Void to appease it. Of course, they're really only helping it along.
Kai'sa
-Kaisa is Kassadin's daughter. You probably already knew that.
-At age 10, her village starts doing...weird shit and sacrificing animals to the "dark powers below". She sets a herd of sacrificial goats free, and they run off into a canyon.
-This seems to please the Void enough, because it erupts, destroying the village and trapping Kai'sa underground. She survives on the debris for a few days, and continues to move deeper and deeper into the chasm.
-Surprise it's full of Voidlings. She kills one with a knife Kass gave her, and after its "death", the creature seems to merge with her. This is the symbiotic suit.
-Trapped for "almost a decade" in the caves (which are not ACTUALLY part of the Void, this is important, she has NOT actually been there), she decides it is imperative to keep the Void away from Runeterra.
-Her name changes from Kaisa to the much more voidy "Kai'sa" to reflect her status of being from "two worlds".
and the Voidlings of Malzahar show me a different thing.