The original Age of Wonders game contains two campaigns, Keepers and Cult of the Storm. There are six possible storylines and four distinct endings. The "canonical" story is the Keepers path, marked in green below. The Keepers and Cult campaigns happen concurrently, and make multiple references to the events of the other. The Cult campaign can presumably be considered canonical where it doesn't directly contradict the Keepers storyline.
The protagonists can be customised, the default is an Elf named Elric for the Keepers and a Dark Elf called Talic for the Cult.
Transcript of the Keepers Campaign (canonical ending)
Transcript of the Keeper Renegade Campaign
Transcript of the Cult of the Storm Campaign
Transcript of the Cult Renegade Campaign
Events in the Renegarde branches (white) are virtually identical between the two campaigns, though the narrator-protagonists will see them with a slightly different perspective. The events of the Lizard, Highmen and Undead branches presumably happen where they do not contradict the other narratives.
Additional Context
The game spreads clues about the backstory of the Elves, Humans and Highmen accross the campaigns, this area puts them together. You can read it now or after the campaigns.
SPOILERS BELOW
Elves and Highmen have worked together accross multiple worlds. The High Men find worlds and fight the Undead who try to consume life, Elves make these worlds habitable. The Highmen want Humans to multiply, because the two races were originally the same, and the most virtuous and enlighted Humans may eventually become Highmen themselves.
Under the terms of a deal, the Elves were supposed to leave the world of the story and give it to the Humans at a point that happened to be the end of Inioch's thousand years rule. However, Inioch and his court had grown fond of their world and refused to leave it. When the Humans began to arrive from their "Garden" world anyway, the Elven Court attempted to integrate them into their kingdom. This failed, because Elven rule was too strict for the unruly Human. More Humans continued to arrive and tensions escalated, culminating in the slaughter of Inioch's Court.