When Lloyd dies there's an animation of stars that circle around his head and he's still sitting up, but clearly not standing anymore. When stars circle around your head usually that means you get knocked out - you become confused and eventually wake up from this.
I think that when Lloyd dies he just has a special corpse. What we can do with his corpse...well I don't know. I think it's just for the sake of design. However, when you read into Lloyd's journal it can tell you maybe something on however you want to interpret it:
#612: Didn't get outside very much. Not at all. Didn't hear much about Boyd. The "mad mage" had an experiment gone wrong it seems. He's nowhere to be seen anymore. Not even in his fortress. I will follow in his footsteps. They just don't understand.
#632: I am holed up in my fortress. I harness its energy. Cosmic energy way beyond anything I have ever seen. I use the lower chamber to build an indestructible armour of power around me. Nothing can touch me. I don't need food, I don't need sleep. Now I can think. I can reflect on the world without it being any nuisance anymore. I don't care who built all this or what its purpose was.
#667: It was built... for me.
For me Lloyd's book symbolizes he was going crazy like his brother, the Mad Mage. He wasn't going to eat, sleep, he just wanted to think without anyone bothering him. He began to think about the world and it's purpose. Then he realized that the world was his and it was built for him. Kind of a behavior where he was just getting maybe a little too alone in his thoughts. When we kill Lloyd maybe he's snapping back into reality and can finally sleep. I know were able to loot him so he does really die... but maybe the book plays a major part in the design of his corpse. I don't think there's a hidden quest to do with Lloyd's corpse, it's just a play on his book. However, this is just my opinion.
Another theory...killing him 5 times maybe he's just really tired and finally gets knocked out poor guy.
Source: https://tibia.fandom.com/wiki/Lloyd%27s_Journal_(Book)