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There is such thing. Unfortunately there is no way to set this value via an item or spell, so the oy thing that can be done is to permanently add it to one of the NPCs, like Viconia.
Well. Giving NPC's abilities unattainable by PC character sounds exactly like IA .Since evil characters are somewhat overlooked it would be fun to give a superbly useful unique ability to Viconia. Could either be "done" (on paper) with a custom made cleric kit tweaked for Viconia (say Priest of Talos - kit with the unique ability of being uninterruptible, "Priest of Lloth") or a Viconia specific item, as she doesn't have one.
Assuming the cleric kits are balanced would give another really nice option for a priest that matches Cernd & Jaheira. This would also continue IA's tradition of making NPC priests more powerful than the PC version can be.
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Making a distinction between Clerics based on alignment sounds like one more thing to consider
For me this makes sense and sort of would also make cleric's more flexible. Say with a shaman in a party there's no need for a cleric who can heal really well, a cleric who can cause damage / buff would be more useful since healing is already covered.