The Mitre of Holiness should, when worn, passively provide a damage bonus against undead and demons you attack.

Wearing the Mitre of Holiness removes the spellcasting penalty from wearing a shield.

Change the Mitre of Holiness’s invoke effect to immediately make another artifact invokeable, zeroing its cooldown timer. This effect also happens passively if it is being worn: if you try to invoke another artifact which hasn’t cooled down all the way yet but the Mitre has, it will automatically invoke itself to zero the cooldown timer of the artifact being invoked so that the invoke will succeed. It gives a message when this happens.

Make the Mitre of Holiness invoke effect give temporary intrinsic energy regeneration rather than a single huge boost of power.