Basically, I have a wizard as a villain who is ambitious, powerful, and has access to nearly unlimited resources. How can I justify giving him any ninth-level spell but not giving him Wish?
Or, alternately, should I just give him Wish, and if so, how do I keep that under control?
A few details that are specific to my case - He's an illusion wizard, he's one of the primary antagonists but almost certainly won't be the final boss, and he's fairly active in the story, showing up to antagonize the players a la Strahd.
The fact that he isn't designed as a final boss character is a big part of what gives me pause re: giving him Wish, but in terms of flavor I'm really struggling to come up with a reason why he wouldn't have that spell.