In Evil Islands, a certain amount of experience gained would be available to boost skills or attributes. There were independent skills (melee, archery, use/steal and three magic classes) where each successive point would increase the price of the next point for just that skill. There were also other skills (weapon expertise, health/stamina bonuses, etc) each with 3 levels, where every level purchased would greatly increase the experience required for all of the other levels/skills.
Spells could be customized, for a price. There were keystones which determined the basic spell type and effect, then runes which could be used to increase the effect, range, area or the number of targets (which should be used with an enemy/ally filter rune), and runes to decrease the amount of stamina required to cast the spell. Each keystone and rune had an associated complexity and stamina, which would limit the number (max 8) and combination of runes available, based on the character's intelligence and ability in the relevant magic system. There were item runes which would allow you to add a spell to equipment, up to its maximum complexity.
This procedure is fairly expensive, and doesn't lend itself well to too much experimentation. Armour doesn't get complex enough to support a spell until the second half of the game, and weapons not until the last quarter.
