The vancian magic system used in Dungeons and Dragons is in itself very safe for the magic user. The caster of a magic spell can rely on it to give a certain effect in the same way a carpenter can rely in a hammer to remain a hammer. A casting of a fireball spell always results in a fireball. Magic users are each day limited to memorizing a number of spells, based on their level, but can newer fail at casting a spell. You either cast the spell safely and the right way or you do not cast it at all.
I don’t really like that. Magic shouldn’t be all that safe. I like to view magic users as metaphysical lawbreakers who bend, break and reassemble the very order of the universe. Magic users use the power of the gods, but usually with much less power, experience and wisdom. They are thus playing with powers that go far beyond their own understanding. Reckless spell-casters, who should be able to stretch their abilities in dangerous ways, should also run the risk of having their spells blow up in their faces.
In my setting, City of the Exiles, magic is something closely connected to chaos, both as world view and metaphysics. You can’t be a magic user and have an lawful alignment at the same time. Clerics don’t use magic, they are instead powered by their divine masters who answers their prayers. Magic manipulates the order of things as an extension of the will of the magician which has inspired many servants of the gods to brand all magicians as dangerous chaos worshipers that should be executed. The more common view is that magic, as dangerous as it is, has it’s uses in the defence of the The Alanu republic as long as it is kept in check by the most arcane and patriotic order of the Magisterium and it’s archmage Alittum. The Magisterium have a special authority extending to all magic users. This authority extends to press skillful magicians into it’s service or summarily executing magic users that are deemed a danger to the republic.
The chaotic flavor of magic in my setting combined with a wish to make magic users a bit more powerful, especially low level such, I have made the table below. Magic users who want to cast a higher number of spells than their level allows may make a roll with the chance of both success and disaster. The referee might also want to use the the table for general spell casting in areas with a very high chaos presence.
Each day a magician can memorize a limited number of spells, in order to be able to cast them. To memorize a spell is much more than simply memorizing the text in a book. The contents of a spell book consists of general instructions in how to build a spell but it must be tied to complex knowledge of the existing order of reality in order to work. When a memorized spell is cast it changes the part of reality it is tied to and therefore it can’t be cast again in the same way. But desperate magicians may try to improvise a recasting of a spell based on their memory of the more general instructions
Table for using spells beyond the level limit. Roll a d6. Add one to the next roll after each roll
1. Spell succeeds.
2. Spell succeeds.
3. Spell succeeds. However, there is also an unexpected effect which can be both beneficial and problematic to the caster. (ex. All water within 100 meters is turned into human blood.)
4. Spell succeeds but the caster gets confused 1d6 rounds and is unable to act other then moving at base rate speed.
5. Spell has the opposite effect.(ex. A healing spell hurts the receiver or heals an enemy)
6. Spell fails and the caster takes either 1d4+level in damage or become unconscious during d100 + 5 minutes .
7. Spell succeeds but the caster is killed.
8. Spell fails and the caster is killed. All within 20 feet take 1d4 in damage.
9. Spell fails and the caster is killed. A hole torn in reality from which it crawls d6 +1 demons that attacks everybody nearby.
10. Spell fails, rocks fall, everyone dies. Everyone within 100 meters from the caster dies in a way that fits the situation. Some extremely powerful beings might survive by a saving throw if it fits the story. All results beyond 10 counts as 10.