I mean, without detail, all you can get is vague suggestions.

With that in mind, I would look into the d20srd "paragon" (I think that's the name of it) mini-prestige class. Have each item grant some (or all) of those benefits. https://www.d20srd.org/srd/variant/races/racialParagonClasses.htm

I've used them a few times here and there for flexible power boosts in one way or another. As prestige classes go, they're kinda weak, but worth considering. But, as a kind of guide to what powers exemplify a race, they're golden.

If your base an artifact off of one, you've got what amounts to a pretty nice boost at any level, but not one that's game breaking.

As an example, have each artifact give the level bump effect you want from the attack bonus and saves, then just tack on the special abilities as whole, or just the ones you want, until you reach the kind of power and flavor you want.

They aren't all equally useful, tbh, but they are all useful.

Since you want historical import, such a council of mages may represent the first attempt to really have cross-species cooperation and understanding. I can't think of anything better for that than a ring of power that literally gives you access to what a race experiences.

If you want to tone things down a little, you could just pull whatever of the racial abilities you want rather than the enhanced versions from the class, but I don't see anything game breaking in there.

It may seem under artifact power levels, but they'd be so broad in scope that I think it would fit.

Besides, powering them up is just as easy as toning them down. Give them the ability to have some kind of advantage when dealing with the race that a specific ring represents, maybe the ability to speak/read their language (where appropriate), and the ability to polymorph into that race at a given level of frequency.