[Tywyll]

Ok, so I've been kicking this idea around for a bit, and at first I was going to discard it, but then I came back to it. I'm thinking I can make it work for my world setting.

First off, I'm using the variant idea of college magic (single skill for all the spells in a group) as that fits the feel of 'Sorcery' in my home brew. Here is what I've come up with so far-

INNATE MAGIC
Innate Magic, otherwise known as Sorcery, is a potent magic that derives from the power of a being’s nature. Otherworldy beings, or those with such beings in their ancestry, can manipulate Mana on a subconscious level, their body acting as a filter, tuning the mana into a specific kind or effect.

New Skill:
Sorcery <type>(0%)-characters choose from a specific kind of Sorcery, based around their mystical ancestry. Typically this would represent their nature, so an Iron Blooded Tryshallan would possess ‘Green Sorcery’, while a Kharic-Dun probably wields ‘Earth Sorcery’ (though don’t call it magic to his face).

Sorcery is an exceptionally difficult skill to learn and master. At character creation it can be no higher than 40/50/75/90 (depending on the power level of the game). Each percentile in Sorcery costs 2 skill points.

A Sorcerer can potentially attempt any spell within their field of magic. Each spell they attempt is rolled against their Sorcery skill, with a -5% penalty for every prerequisite spell that it would normally require (per Gurps list). Spells cost a number of MP equal to the normal fatigue cost . Effects cost an additional 1 MP for every 2 full prerequisite spells they possess that the caster lacks skill in. Each spell the character has currently operating is an additional -5% to their casting skill. For example-Elith the Green Sorcerer wants to cast walk through Plants. He has no spell skills, just Sorcery at 40%. Walk through Plants has 6 Prerequisite spells, meaning it will be cast a -30% and cost an additional 3 MP. Even using Ceremony, he can only raise his chance to double, or 20%. Good luck! If he knew Hide Path and Heal Plant, that would reduce his penalty by 10% to a -20%. Using Ceremony he could then increase his 20% to a 40%. A bit better of a chance.

Sorcery cannot be improved with experience, and it takes twice the normal time of study or training to increase (so a character with a 30% in Sorcery would have to spend 60 hours in training before they would see a potential benefit).

Sorcerers can choose to learn spells. Learning a spell takes 50 hours of research/contemplation x the number of prerequisite spells (so the Walk through Plants spell would require 300 hours of research). If trained by someone or something that knows the spell, this study time can be reduced by ½. Alternatively, a Sorcerer could manifest a spell spontaneously, though this is costly (in Hero Points-it costs one HP per Prerequisite spell). Once a character has learned the spell through whatever means, it begins at a level equal to their chance of casting the spell (i.e. their Sorcery skill -5% per prerequisite spell, Elith could learn Walk through Plants at a base 10% chance, or 20% if he knew the other two prerequisite spells). The advantages of spending the effort to master the effect are that Spells can be improved with experience, training time on spells is normal, and the cost in MP is reduced to whatever it would normally be. If a Sorcerer’s Sorcery skill improves after developing a spell, it has no effect on the spell. Starting Sorcerers can buy spells at a 1 for 1 in skill points, based off their final Sorcery Skill.

Other Casting Modifiers:
Gestures with only one hand: -10 percentiles
no hand gestures at all: -20 percentiles
Softly spoken incantations: -10 percentiles
no incantation: -20 percentiles

When a Sorcerer’s skill reaches 75%, all costs to cast and maintain effects are reduced by 1. At 100%, and every 25% additional skill, they are reduced again. This can reduce the cost of a spell, or its maintenance, to 0. Remember, however, that there is a progressive penalty for every spell you maintain.

Skill Effects-
Fumble: The caster loses their next action and all the MP the effect would have cost.
Failure: The caster loses a single MP.
Success: The spell takes effect as normal, and the caster spends the normal amount of MP.
Special: The spell takes effect. Temporal spells have their base duration changed to multiplied by 5. The spell costs ½ MP.
Critical: The spell takes effect at a cost of 1 MP. Temporal spells have their base duration multiplied by 10.