Seekers of the Misty Isle
Your religious rites require elaborate gestures that cause you difficulty when casting divine spells while wearing armor or using a shield.
Prerequisite: Ability to cast divine spells.
Effect: You suffer a spell failure chance (due to armor, shields, or anything else which causes arcane spell failure) when casting divine spells, just as if they were arcane spells.
Source: Dragon Magazine #326 (Class Acts – Flaws For Clerics)