This prompt is a little dark since it involves the main character’s wife trying to kill them. At the same time there is some humor in the fact that the main character can’t die and is actively just letting her go ahead and try and do that. Can you imagine what that looks like?
Wife puts something poison into the main character’s drink and hands it to them. “Congratulations on that deal you just completed. I’m so proud of you, Honey.”
Main character drinks it and nothing happens. The wife is so confused.
A other time maybe she hires a hitman and the main character comes back unharmed and she just doesn’t understand how this could happen. The hitman she hired was supposed to be the best.
Even more confusing is the fact that the hitman comes to her for payment on a job completed and is absolutely shaken when they learn the main character is alive and well, because no one could survive that. It’s just not possible.
Being immortal, it’s not surprising that this character would have amassed a lot of money. You can earn a lot of money if you have centuries to do it in. Undoubtedly they have seen all sorts of things come and go and it is likely that not everything they tried worked.
Another interesting thing here is the term immortal. While it does implied to people someone that will not die, it rarely actually means someone who won’t die. Usually it’s someone who doesn’t age and won’t die to sickness or old age, but is susceptible to other things, such as getting their heads cut off, a wooden stake to the heart, or the blood of the golden hind.
Given the wording of this, it makes it seem likely that the main character is actually immortal, but that is entirely up to the author. Maybe in the end there is something capable of ending their life or maybe not. What do you think? Would you give this character a way to actually die at the hands of their wife? And if you did, would you let her kill them? Or would you have something else in mind?