Lloyd is very very good guy. They were lovers and very open like everyone in Kalak know about them. Glenburg House & the current ruler of Kalak are very suspicious. They purposely giving medicine to Slan that eat away his memories specifically when it related to the time Slan was a Kalak Lord and anything related to Lloyd
I couldn't find the novel so Idk much past the translation but my hypothesis is. People in power didn't like Slan as Kalak Lord, while normal subjects of Kalak actually like him. I think these people in power put something strange in Slan, idk maybe magic or that supposedly bug inside his head. Slan went mad (like he suddenly had mania), and accidentally killed his father. With this reason, they can remove Slan from power, they can't killed him so they said they will make Slan as slave temporary.
What's weird is the current Lord of Kalak is actually relative of Glenburg House.
I think Slan is just good nature guy, he was friend of Lister and he respect Lizbeth as knight. Glenburg is distance relative of Slan but also vassal family. Because Lister mentioned something : I m no longer your subordinate.
My guess is, Lister is jealous over Slan & Lloyd relationship, so he purposely tormented Slan.
It’s gonna be like a forbidden lovers trope, or if the brown haired guy is gonna turn out bad in the end. Cause he seems too good to be true, and at times very suspicious