So I recently started a new campaign, and decided to do magic a bit differently. In the Xiombal setting, magic-users are called sorcerers, they get a different system for casting spells, rather than memorizing spells then forgetting them when cast, they keep them permanently

Each sorcerer can cast a number of spells per day equal to their level. So a 5th level caster, Rinook the Blue, can cast 5 spells per day of any level. For ANY spell, when they find it they roll to “know” the spell, based on their intelligence

They also add a 1% chance of success per level of experience. So for example, 5th level caster Rinook the Blue has an intelligence of 16, and a 70% chance of “knowing” any spell, regardless of spell level. If the “to know” is successful, the spell is permanently in his mind

If unsuccessful, the spell can only be cast once from the scroll. Also, when cast, the sorcerer’s odds of success are equal to their “to know” odds + 1% per level. If the casting is unsuccessful, then the spell has harm odds equal to the spell level x 5% - 1% per caster level

An example. Rinook the Blue finds a scroll with 2 spells, magic missile and wall of fire. He rolls a 83 for his first roll, so he does not “know” magic missile, he can only cast from the scroll. He rolls 50% for wall of fire, so it is now permanently in his mind

Now, say he was in a combat situation and cast a wall of fire. First off, he has a 70% chance of casting it successfully, say in this case he rolled a 77%, so the spell fails. Now, he has a 20% chance of harm from the spell - 5% for his level, so a 15% chance of harm.

So overall when he casts a wall of fire there is a 30% x 15% = 4.5% chance of harm. Not large, but not trivial either. If he obtains a harmful result then he would experience the wall of fire damage on himself. Ouch.

There is only one way to save yourself if you obtain a “harmful” result from the spell casting, you can use your force of will to shut down the spell before it gets out of your control, but to do so you lose a point of intelligence permanently.

What I like about this system is that the odds of failure/harm are low enough to tempt casters to use dangerous magic, but high enough that they will sooner or later roll badly, and there is a good chance they will die if they do so.

This one change, adding failure/harm odds to regular casting, has significantly changed the flavor of magic in this game world, suddenly every single use of magic holds the potential of being harmful

The increased power of the sorcerer (her chances of success are not tied to the spell level) is balanced by the increased risk. The only limitation on the system is that the most spells a warlock can have permanently in their head is equal to their intelligence + their level.

This means they need to think a bit about which spells to try and “know”, but it eliminates the need to plan out which spells to memorize each day.