I wanted to have a plot hook in my game with a wizard that reincarnated, but with total amnesia. Is there any way to do this with the rules as written?
Yes have a wise NPC say it sometimes happens in rare cases.
The GM is the law of the game.
I'd say that about covers it.
For things like this just invoke Rule 0.
I make it a point to have this discussion with all players of every group I play with. Story trumps rules, always. For those that don't like that, they can find another table to play at. In all my years of GMing so far, I've never had more than a passing disagreement with any player where story trumping rules was concerned.
That said, there are some possible (modified) mechanical ways you can go about this. The spell Modify Memory has limited use, but a master caster could more than likely research and design a spell that is much more powerful. Of course this raises the caster level of the spell, but all of that is clearly within the researching and designing spells mechanics.
Hopefully this helps you move forward with a great plot hook, so your campaign is as exciting as you and your players want it to be.
I actually like this idea a lot. While amnesia can be a cliche, what event could bring it on more than being violently thrust into the clutches of death, then violently ripped back out? I like it.
At my games there are slight memory gaps for the returning soul. It's a bit more flavourful instead if I've paid my gold now I'm back from the dead, all in a days work attitude some people get.
There was a 9th level spell named Programmed Amnesia in 2E (Spells & Magic sourcebook) and it was updated to 3E (Spell Compendium p. 162 or Complete Arcane p. 118).
But then again a wish spell could cover it too.
The idea is that the group is going to meet a very high level female wizard that is seeking her long (a few hundred years) dead lover. The lover was a Lich (very evil) who's philactery was destroyed. But, when they were younger, the soul had a spell of reincarnation bound to it. So when the soul was freed from the phylactery, instead of simply being gone, the soul was reincarnated. She's travelling to the land that the characters are originally from and in the process of moving away from.
The hook is that the lover's name is the exact same name of a hero that's an oracle that is also very high level and is said to have been found, in his early adventuring days, as an adult (of a different race than said wizard or lover) with no memory of his childhood.
I'm working off of the idea that the soul was not tainted from it's earlier good version and acts due to the binding of the reincarnation spell before. What came after that literally isn't a part of the character any longer.
What I'm really hooking this onto is that said high level oracle is basically the founding father of a new nation and the group is already suspecting there's an evil group working within the new political groups to try and take power from the foundation.