Yes, I've been assuming that; as if restoring magic is not the goal it's simply a no-magic campaign and that's that.
Or, it's a campaign that's about things other than magic, because, except in this one case, the magic went away.
Fair enough. Here I'd say that if anyone's to become the "first mage" it should probably be an NPC, specifically in order to prevent one PC from being or becoming more important than the others (again, the exception here would be solo play).
But why assume that the only type of adventure in the setting is going to be about the last mage? A good GM will be able to make every single character important, even if one of them is "the only one of," "the last of," or even "the chosen one."
I actually played a chosen one, once. She was a cleric who literally had two different gods fighting over her, and she was a character who had the longest backstory I have ever written for a character. Out of a campaign that lasted for several years' worth of weekly sessions (with the occasional hiatus for other games or days we couldn't play), I maybe had four sessions truly dedicated to this status. We spent longer than that on sessions that were nothing but political negotiations that my character had nothing to do with but let certain other PCs take center state. The rest of the time, when my character had the spotlight, it was because of her perfectly normal, non-chosen one-related activities, such as clever use of spellcasting.
So don't assume that a last mage is going to always hog the spotlight unless either the player or the GM are bad at their jobs.
Good point. I have been assuming that, yes. But if magic isn't benevolent and-or desired and people are welcoming its demise then the player of the last mage is again not going to have much fun, as the rest of the party might well be justified in killing it as soon as they find out what it is.
Then they miss out on learning that the reason magic isn't seen as benevolent or desired is potentially pure propaganda. Or they miss having a moral dilemma as to whether to use magic that might be evil. Both of these things make for very good roleplaying.
If your intent is to keep something safe it's just a bit counterproductive to take it out and expose it to risk, hm? And unless the party want to spend their adventuring careers doing nothing but guard the last mage in her glass bubble, they're likely going to go off elsewhere and leave said guarding duties to stay-at-home guards.
The PC is their own character; it's up to them to decide if they want to be kept safe.
Or, you and that player work out a deal where your character is their bodyguard and tries to keep them safe, while they look for and often succeed at ways to sneak around you--this is a common media trope, after all.
It's one thing if a player is choosing to do things that have been agreed upon to not be in the game, such as if the table said "no sexual assault" or "no real-world racism or sexism" and the player insists on bringing those things in. But telling them they can't play their character only because you decided so? That is
bad. They're just trying to play a character and you're poo-pooing the idea for reasons that don't work
because they're a PC, not an NPC. I have to say, if I were playing in a game as the last mage, and you tried to literally force me to not adventure even though I wanted to, I would either leave the game or ask the GM to kick you from the game. Because that idea of yours would cross the line into harming another
player's ability to play the game.
Put another way, the player who wants to play the last mage probably hasn't thought the ramifications all the way through.
Or, they thought of the ramifications for the game world but not for ones related to an overstepping fellow player.