So after a failed sanity check on my part concerning the special attacks / spells that target abilities, I ran into a bit of confusion.
Ability drain reduces a stat, essentially forcing a rebuild of the character to account for it, in contrast to the ability damage (which stacks upward like nonlethal damage or negative levels) and ability penalty (a variety of untyped debuffs which work like ability damage.)
So let's suppose I'm a sorcerer, 16th level, 18 Charisma. LOW, I KNOW, but just by way of example. I know summon monster 8.
Now I take some attack that deals 1 Charisma drain, forcing me to rebuild to apply the effects of an actually reduced stat. While I'd say "luckily, it's Charisma, only need to adjust skills," some of us heretics actually cast from Charisma. Heresy, I know.
- Since I'm not allowed to know SM8 at my current Cha score, do I suddenly forget it?
- If I get restorated later on and regain my ability to know 8th level spells, do I "get SM8 back" or am I making a fresh pick, which could include picking SM8 again?
Also, related questions for if a similar thing happened to Intelligence:
- If I get restorated, will the lost skill points go back to where they were lost from, or can they be allocated again?
- Would I lose "knowledge" of the 8th level spells in my spellbook?
- If I get restorated, will I have to go through the spell-learning process in order to regain those spells? And also, would I have to transcribe them into my spellbook?
The sanity check, of course, would be to treat ability drain like permanent negative levels; but that's departing from RAW, and the previous battery of questions is about RAW.
It's not that you're not allowed to know it as much as you can no longer cast spells of 8th level.
I would argue you don't lose knowledge of those spells, nor do you get a "free rebuild". When you're ability points are restored everything returns to you as though you had not taken the ability drain.
Regardless of RAW, I absolutely wouldn't allow a player to rebuild because as I can imagine people deliberately tanking their stats so they can rebuild their character freely.