Adding Common Item Effects to Existing Items
One of the most frustrating roadblocks to using interesting, unusual magic items is that they take up body slots that you need for an ability-boosting item (such as gauntlets of ogre power), a ring or protection, or another must-have item. To address this issue, Magic Item Compendium presents official rules for adding common item effects to existing magic items.
Table 6-11: Adding/Improving Common Item Effects presents a list of common item effects, from ability score enhancement bonuses to energy resistance, and the price to add that effect to an item.
The table also indicates the appropriate body slot (or slots) for each effect. For example, you can add an enhancement bonus to Charisma only to an item that occupies the head or shoulders body slot (such as a headband or cloak). A DM can choose to deviate from this guideline, but should avoid nonsensical combinations (such as gloves that provide a bonus to Wisdom).
Adding one of these effects to an existing item works much like creating an item from scratch. The crafting character must meet the given prerequisites, must expend gold equal to one-half the price and XP equal to 1/25 the price, and must spend 1 day per 1,000 gp of the price.
Example: Lidda has a pair of boots of striding and springing, and she wants to add a Dexterity bonus (rather than buying gloves of Dexterity). Her friend Mialee isn’t around, so Lidda must track down a stranger to do the work. She pays the wizards 4,000 gp, and four days later her boots now also grant her a +2 enhancement bonus to Dexterity. When Lidda later decides to improve the bonus to +4, she manages to talk Mialee (who has the Craft Wonderous Items feat and knows the cat’s grace spell) into performing the work. After spending eight 8-hour days of work and expending 6,000 gp of components (likely supplied by Lidda) and 480 XP, Mialee succeeds in increasing the +2 enhancement bonus to Dexterity to +4.
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