All magical items have some sort of magical aura (be it essence, channeling or whatever). To successfully use these items, the user has to attuner to them.
The following refer to Difficulty tables:
*trivial* *routine* *easy* *hard* *very hard* *absurd* *sheer folly* *phenomenal* *preturnatural*If you see some there you didn't know of, look at RM2 Companion IV.
Basic items: By which I mean simple pluses, and nothing else.
Weapons (Non-intelligent): By their nature, they are made for warrior types with next to no magical skills whatsoever. So they are made to be *trivial* to attune.
Armour (Non-intelligent): The same as above.
Skill modifiers : E.g. boots of climbing, braces of defense, etc. Very simple items. These all fall under the *easy* category. They are a little more difficult to make than enchanting a weapon or armour to be +5.
Intermediate items : The basic items with more stuff, or anything to do with altering magic (multipliers, spell adders etc.)
Weapons (Non-intelligent): Plus items with something else, maybe an extra crit or some strange ability (teleport, healing, etc.). These sorts of things are still made for the warrior types, so their attunement is *hard*.
Armour (Non-intelligent): Plus items with something else, maybe crit negation, or something like heat resistance. Definitely warrior types, so *easy*.
Skill Modifiers: Either more advanced bonuses, or groups of skills. *very hard*.
Spell Adders and Multipliers: Yes, I make my mages attune to these items. I know it might say in RMSS spall law not to do so, but I refuse to let mages share their stuff. The category depends upon the * or + number, and on the level of the spell that these items will work at. I have an additional rule that adders and items also come in level ranges, e.g. a +1 adder that can only be used for 1-5th level spells, and the *2 multiplier that can only handle 3PP (Multiplied to give 6 PP spells). I don't allow PP multipliers over 3 in my game.
Magic using items: e.g. Wands, Staves, Rings, anything with one through five effects/day. By effects, I mean that one spell can be used five times a day, or five spells once a day. Note these are SET spells, not like spell adders. Very hard to make, and costly. Not for everyone *very hard*.
Complex Items : Artifacts, and Intelligent items.
Anything intelligent would have its own resistance to being attuned to. Say for instance that Borik the Chaotic Lord found a mace (+20 Holy crits, 150 Will: command kill undead) and tried to attune to it. I think the intelligence inside the item could somewhat resist. But if Nelob the Paladin tried to attune, then I think the item would actively help him.
So diametrically opposing outlooks (uses for the item) will be *phenomenal*. Almost the same (i hesitate to use the word) alignment *absurd* Exactly the same outlook on life *hard* (even the same outlook doesnt mean the same methods - take the above example of command kill undead. So the paladin finds himself killing undead all over the place. Then these 30 or 40 Vampires decide to take him out. He'd rather run away and get help, but the item would have none of it).
So what I do is add/subtract the will of the item from the attunement roll. Note that with super-characters (or will increasing magic) an evil person could attune to a holy item, but would still have to enter willVSwill contests every time he wished to used a power, or even use the item as a weapon.
Artifacts without intelligence (or buried intelligence, or even unconcerned) are always so powerful they are always *absurd*.
There endeth the lesson.