Starting in on the Immortals Set (no, haven't really read much past the last post, I've been busy) got me thinking about how to implement artifacts into Treasures, Serpents, and Ruins. Since I had just finished up the magic items section for TSR-East, I went on in and started in on the artifact rules.
In BECMI, artifacts are an extension of the Immortals rules, since they're created by immortals. They run on immortal power points. The powers are classified and ranked by power points needed for the effect.
In AD&D, however, they just have certain numbers of powers at certain levels of efficacy determined by the DM. The lists are just by power level.
In both sets, in addition to their powers, artifacts have negative effects on mortals that wield them. They also have a history and a purpose.
So in my rules, I decided to split the difference. Artifacts in TSR won't use power points, and will instead follow AD&D with each power: providing a constant bonus, being usable at will, or being usable a certain number of times per turn, hour, or day. But the powers are classified as Offense, Defense, Knowledge, and Utility, and artifacts are limited in how many of each type they can have by their power level.
And since I hadn't included intelligent swords in the regular magic item rules, I made them the lowest power level of artifact. And I extended the intelligent weapon rules into artifacts, so if the artifact is intelligent (not all are), it has Int and Ego scores, personality, and a desire to enact its purpose or indulge its personality traits if it takes control of its wielder/owner.
I'm currently in the middle of writing up power lists, and will be moving on to the drawbacks/limitations soon.
This is pretty fun.