Below are some Alternate Rule sets the GM can add into the game. This can include alternate ways of casting magic, and other such variants.
A vast wasteland filled with miles of uncharted land. There is very little variation in the plane’s climate or biome, the ground a dull light purple and the skies a dark metallic silver with a single bright red sun illuminating the landscape or at night a blue moon arises. The Plane of Corruption twists and contorts that which comes in contact with it; people, magic, animals, and plant life alike are torn and tampered with.
Those who come in contact with the Plane of Corruption must make a Fortitude save (DC 20) or take 2 points of Constitution drain. For creatures without Constitution, they gain 2 negative level instead (successful save negates). The 2 points of Constitution drain remain in effect while the character is on the Plane of Corruption and can only be removed once they leave the plane itself.
This type of magic comes in two forms: that which manifests corruption itself, and that which is diluted by the power of corruption.
Manifested: Magic with the corruption subtype is unaffected when cast upon the Plane of Corruption, and draws strength from the energy around it giving it +1 Caster Level when cast.
Diluted: Spells that are being interfered with by corruption energies tend to become erratic and may harm others. The caster must make a concentration check (DC 15 + Double Spell Level)
Through the destruction of one’s body and mind, spells can be enhanced for a price.
By dealing 1 point of damage to themselves, the caster can cast non-corruption spells on the Plane of Corruption without penalty. By dealing a number of ability damage to themselves equal to the level adjustment of the spell (minimum of 1) they can use a metamagic feat without increasing the level of the spell or casting time.
The caster can give themselves a -1 on a single skill check for the rest of the day to grant themselves a +1 to hit with a spell. This can be done up to a -10 to their skill. Alternatively they can use this same method to heal HP or ability damage. For every penalty to their skill checks added, they gain a point of HP up to a maximum of -20 on the skill and +20 HP. For every 4 points of penalties added to their skill check, they regain 1 to their ability score. A caster doing this can repeat the effects by selecting a new skill to impose penalties on.
Subsets of skills cannot be chosen. (One can impose a penalty on Craft, but not specific Crafts.).