Incantation-Based FX Items
Making most magic items is a solitary endeavor, one in which the spellcaster spends days (perhaps weeks) preparing an item to receive and permanently hold a spell. It is possible to do the same thing with an incantation, but this requires the help of secondary casters. This has a greater chance of failure than infusing an item with a spell as the process requires both a Craft check and the appropriate skill check for casting the incantation.
The person creating the item must have the appropriate item creation feat or ability (such as the Mageís Scribe Scroll ability), spend the appropriate amount of time fashioning the item, succeed at the required Wealth check (purchase DC = one-fifth of the itemís listed purchase DC), and spend the appropriate amount of XP. Then the creator must succeed at the required Craft check. If this check fails, the materials are used up but the XP are not spent. If it succeeds, then the item has been successfully prepared to receive the incantation.
The person who created the item must then serve as the primary caster in performing the desired incantation. This occurs as written in the incantationís description. Failed incantations have all the usual repercussions, plus the item has been tarnished and must be prepared before another attempt can be made to infuse it with the incantation.
Determining the Purchase DC
Calculating the purchase DCs for items created to hold incantations is technically impossible, as incantations have neither caster levels nor spell levels. For the purpose of calculating and itemís purchase DC, use the following conversions.
Caster Level = 5 + total number of successful skill checks required to complete the incantation (minimum 11).
Spell Level = total number of successful skill checks required to complete the incantation.