All Magic Users (and only magic users) in my campaign have the inherent talent to read and control magic for their own use. Generally, this is limited to the magic user, his own items and knowledge. However, mages also have a darker, more dangerous power which can be used with great care.
Unfettered Magic
Level: 1 Components: V, S, M
Range: 3" (30 feet/30 yards) +1" per level Casting Time: Instantaneous
Duration: Instantaneous Saving Throw: Special
Area of Effect: One Creature
All magic users have the ability to defend themselves from magical forces, by the nature of their studies in their profession. Unfettered Magic is a dangerous defense against hostile magic users. The danger comes in respect to the possible level disparities of the defender and attacker.
A magic user can only cast this spell when they see another magic user begin casting a spell with a Casting Time of one segment or more. It cannot be cast in preparation - I.E. before the other caster begins.
As soon as the last symbol and word for Unfettered Magic is uttered and woven, the other magic user is entitled to a saving throw. If they are successful, the caster of Unfettered Magic also makes a saving throw. What happens next, depends on these rolls.
If the defender makes their roll saving, the caster of Unfettered Magic must make a saving throw to avoid taking 2 points of damage per level of the defender's spell. If they are unsuccessful AND they do not have enough hit points to survive this damage, they are burned to ash and the extra damage explodes in a 1" (10 feet or yards). People in this area must make a save for half damage. The magic user can't be revived to a corporeal form by any means short of wish. Casting resurrection or reincarnation will summon their ghost.
If the defender loses his saving throw verse Unfettered Magic, they immediately lose the spell they are casting and the caster of Unfettered Magic gains this spell, in all ways. They can cast it before the end of the round. If they survive combat, they can scribe this spell into their spell book. If they do not transcribe the spell within 24, they forget it. The magic user is not required to cast this spell at all, they can merely release the energy.
IF both magic users make their save, no damage is taken, but the caster of Unfettered Magic has his position revealed and is now know to be a hostile spell caster. The other caster has the option of targeting them immediately with their current spell instead of casting at their previously selected target. Range and area of effect may preclude this.
If there is a level disparity, say a 1st level magic user trying to divert a 5th level spell, the user of Unfettered Magic takes one hit point of damage per level of difference. For example, a 1st level magic user gains Magic Jar, they would take 5-1 points of damage, regardless if they used the spell at all. If this reduces their hit points to zero or less, they die. In this case, they can be revived by normal means and there is no explosion as the energy was directed inwards. Note: even if the caster dies, they may direct this spell before the end of the round.
When a magic user uses the Unfettered Magic spell, there is a cool down period where they may not work other magic. The duration of this is based on the level of the spell they attempted to seize. It is one round per level of spell. Redirecting a 7th level spell will result in a 7 round period where the magic user cannot use magic at all. While magic items will continue to function if they function continuously, like a +1 dagger or ring of protection, the magic user cannot use a wand, staff, rod, potion, or cause a miscellaneous item to activate. This limitation occurs on both success and failure.
Unfettered Magic can only be used on actual spells, cast by a magic user. It does not work on clerical, druidic, or illusionist magic, nor can it be used against spell like abilities or magic items, such as a wand of missiles. Non-magic user casters accidentally targeted by this spell will immediately know the location (even if hidden) of the magic user and have a choice to redirect their current spell on to them.
Since most low level magic users have relatively no chance of forcing a higher level mage to fail a saving throw, this is a desperation move, where death is better than not trying. Oft-times, low level magic users will do this when they are within 30 feet of a higher level caster, in the hopes that the explosion will hurt them. Higher level magic users can use this spell with virtual impunity but generally don't because of the cool down.
This Worldographer map is from my current campaign on the Peninsula of Plenty. Each hex is 6 miles and the characters are following the road along to the coastline. 
