The only thing about Wish is that screwing with player’s Wish seems cheap to me. “Oh, just fast forward then to a time when the bad guy is dead, ahyuk.” Gigax spent so much time in 2e in the description of Wish explaining ways to screw it up it’s unreal.
If that’s going to be the case, why even bother having it in the game? Let it be a Wish. Just, you know, you have to roll a d6 afterwards. Rolled a 1 or 2? Can’t do it anymore.
But what I did worked great, cause it lets them have their Wish. One character is a Dragon Sorcerer, so her Wish was to be a full Dragon. So I gave her the ability to cast True Polymorph once a day to only become an Adult Blue Dragon. She is allowed to keep all her class abilities as a Blue Dragon.
Do I worry she’s overpowered? Not really. One character is a Swords Bard. His Wish was the ability to declare one roll a day to be a nat 20. After I said ok, he took a Vorpal Sword as his main magic item.
They’re all overpowered. They’re all godlike. And that’s the point. At this level, LET them be overpowered and godlike. There are plenty of creatures that can scare them. Including the bard with the Vorpal Sword, who jumped on his broom of flying and took off THE MOMENT the rust monsters showed up. There’s always ways to make it interesting.
The original rule for Wish was that they already cast it and can’t cast it again. That was when the game was supposed to be a one shot. My new rule is that they can only benefit from one Wish per source of Wish. So if they get a Ring of Three Wishes, each person can only use it once. Some beings, like Genie Lords, count as their own Source and can cast it on someone’s behalf once per person, but a PC that gets Wish as a spell can only cast it one time.
It’s made Wish into something to be respected. If you can cast it every day to duplicate a spell of 8th lvl or lower without material components, you’re basically a god, and I didn’t want to deal with that. Seriously, the spells you can abuse that way.
My second rule is that if you wish for something too outrageous, instead of getting it handed to you, you gain the knowledge needed to make it happen. Wanna become a Lich? Great. You now know the process. Lots of ingredients, lots of quests, and then you can be a Lich. Want to kill Tiamat for good? Great. You now know of a sacred sword made from the heart of a dying god, deep in an endless dungeon with the power to absorb the divine spark of a deity. Put your helmet on, cause it’ll be rough getting there.