Does anyone know why Llanie's amulet was able to kill McMorn? Was there an explanation in the game or was it just convenient? I thought he amulet was supposed to revive the wearer if he gets killed or something.

It is just another example how this game confuses the player. Llanie said that amulet's true powers only work when the wearer is pronounced dead, she never said what it actually does. When you attack MacMorn he laughs at you and says "you are already dead" and that is it, you don't actually have to die, someone just has to say it. I wouldn't guess it in million years, especially in this game where you actually die in every second scene.

I solved this by good old "try everything with everything" and only after I saw what was happening I understood its meaning. A smart puzzle, but feedback to the player could have been better. I wish Llanie's words (and in general all crucial information about inventory objects) could be remembered in dialogue or inspecting the item.