The stoneskin spell can only affect the caster. It causes his skin to become as hard as granite, causing all blows to glance harmlessly off his body. This invulnerability lasts for a number of hits equal to 1/8 of the caster's intelligence score. After the spell expires, the effect is instantly dispelled and the caster's skin returns to normal. When cast by magic items, this spell lasts 3-4 hits.