the regalia of evil from the book of vile darkness. it consists of three items (crown, scepter, orb). put together, the items grant theit possessor additional improvements.
it's not exactly as in the book though because nwn doesn't include all the spells and feats, but i tried to stay close.
there comes a script with the items which handles their OnAcquire, OnUnacquire, OnEquip and OnUnequip functions. it is important that all three items get the same tag, and that the script also has that name.