I don't know how much actual lore there is.
Theory:
Besides Zemo, Khazard was one of the few active Mahjarrat.
Khazard opts to try to "retake" lands once held by him and Hazeel. He knows he is in no position (atm) to take Ardougne. He figures the Tree Gnome Village would be a soft target.
He first establishes the Port as a his first base of operations. He does have some followers, but tries to recruit more. But the quality of what he gets is more "thug" than "soldier".
He has a secret talk with King Lathas. Lathas has a WW2 type agreement between German/Russia regarding Poland. He won't interfere with Khazard since he is focused on the threats in the Pass. Khazard will 'cede' some territory allowing Ardougne to expand southwards. Lathas will diplomatically stall the gnomes. And he figures if Khazard's forces ever become an issue, he can still eliminate them (or make a last second alliance with the gnomes.)
Khazard attacks the gnomes. It is not a quick victory. Time passes, he gets bored. He creates his Arena. Locals go missing, but no one does much about it.
Khazard more or less withdraws from the War letting his "army" deal with it. He entertains himself more with the events of the Arena and making longer term plans like how to revive Hazeel.
Eventually the events of Fight Arena and Tree Gnome Village occur. Then the Shadow Sword miniquest.
Then Hazeel takes part in the last Ritual.
Renewed by everything that has happened, he begins to take a more active past in the Gnome-Khazard War again, even though things on the battlefield don't improve.
The war is still stalemated as he doesn't have the army size or resources he needs. But his goal has shifted. The 'battle' is now more of a training ground to professionalize his forces for Zamorak.
The gnomes can wait.
11-Aug-2020 12:22:48