Fixing Casting Tablets

So, casting tablets... tricky issue. While some people feel that the possibility to case some spells without having to actually re-invent them makes the game more accessible, as it stands right now casting tablets are extremely "powerful" - as in that they raise the question why magi would even bother with learning some specific spells as well as why there is no abundance of high-level general spells that see a lot of use (Aegis of the Hearth, circular wards, etc.), given that casting tablets can be copied like lab texts. Also casting tablets don't require any extra time for casting and thus are really infringing on the playing field of formulaic magic.

I had an interesting idea yesterday: Casting a spell you don't know is spontaneous magic, so why not handle it that way and have casting tablets give a bonus to that? Using the rules for ceremonial magic seems like the best idea, given that you have to cross-reference the instructions on the tablet in order to benefit from the bonus. Therefore casting tablets take longer to use and don't make sense for any spell anymore. Casting a Pilum of Fire that requires an hour of preparation? Unlikely. Casting Purification of the Festering Wound? Casting tablets sure come in handy there.

The only question to me is what the bonus should be. Several ideas:

  • +1 per magnitude of the spell. Works nice and simple mechanically, but raises the question of the in-game logic of it. (It's a plain 10% reduction of the base ease factor, so it might be justified as plainly being "easier" to cast.)
  • A flat +5 bonus.
  • A bonus that is set while writing the lab text, making it harder to write the higher the bonus is (+1 per 1/2/3/5 levels of the text over the level of the spell?). Probably open to abuse.
  • The sum of the Artes Liberales plus Philosophiae of the writing magus. (Might also serve as a cap for the previous option.)
  • ...?

Another option that might be added is that casting tablets reduce the time for ceremonial casting from 15 minutes per magnitude to 5 minutes per magnitude.