I like your Ring Of The Crucifix example. I can definitely warm up to the overall concept *IF* these items are unique and part of a completely random pool on a per play basis. If they are not, then I would definitely prefer items that bestow buffs or penalties on a general 'class' basis - by category of ability than by specific name. In that latter instance, Ring Of The Crucifix might offer protection versus the Dead and Spirits wielded by The Oak and The Vampire Lord, but not limited to them. As Annatar11 stated, setting up the logic for the sense of an item is preferable to making something function on a more specialized "because" basis.
Protection Versus Stun
(decreased duration/chance of stun, paralysis, and freeze abilities; or % chance to ignore effect)
Protection Versus Decay
(decreased damage from disease and death abilities)
Protection Versus Fire
(decreased damage from fire abilities)
Such items have the real potential to be more applicable versus or in the hands of certain Demigods over others, yet can be so without being rigidly/blatantly forged to be so. Items that curtail Thorn effects and Life Drain effects have similar potential in light of enemy item purchases that grant such as well.
I would add that any specific target item should apply its effects only to the wielder - this preserves the newfound battlefield role of the user versus its target. Exerting auras means bestowing beneficial countering effects to all around, which would defeat the purpose of the item being unique & singular and therefore limited. You would not want a single item user to apply its effects to every ally around him - that would be too useful, unless the effects were more subtle/minor in nature.
Generally I speak of protections rather than enhancements simply because such things strike me as safer to ponder and weigh than substantial boosts to damage and the like... maybe a bit easier to judge right now. After all, toss in too many percentages and multipliers and you may wind up delivering 10s of thousands of points of damage per hit (!).
You *could* administer effects to categories of Demigod by specific Demigod as you alluded to above in your code possibilities Frogboy, which would serve the same end as applying more general effects to those who fall under the classification of those entities who are indeed affected by the item. You might say what is the difference... the entire point of a game is the illusion of accomplishment. Key to the illusion is perception. If my perception is that 'X' item is simply a gimmick lever by which 'Z' character can be defeated, the illusion of accomplishment suffers - I will simply have fulfilled a prescribed task, much like a linear puzzle. Demigod is dynamic and action-packed, not a puzzle to be solved with the correct purchase. I want to play this game, and item equipping is just a part of that equation.
So I guess I sum up by supporting more specialized items *if* they are unique and randomly assorted along with every other item, but prefer simply category-based items that can serve much the same purpose without being exclusive.
A Vampire Lord - I suspect - who stocks up on additional Life Drain items would be withering, unless an enemy confronts him with Grail Armour that cuts in half any enemy Life Drain ability %. The effect of having specific uses against specific Demigods & entities is there without having to be specific about the target... it just follows logically.
I`d certainly be willing to try what you come up with - the point of a Beta (!). You folks have had good judgement so far (!)... . Thanks for listening; btw, this and Sins Of A Solar Empire have been the best betas I`ve ever been in.