there's an old little used idea in astrology that each planet has a certain affinity for a certain planetary aspect, based on its sign of rulership's position to Aries. Thus Mars, ruler of Aries, has qualities of the conjunction aspect(and/or vice versa), Venus and Neptune have qualities of the subtle semi-sextile, Mercury and Uranus the communicative sextile, and so on...(in modern astrology each sign tends to have a day ruler and a night ruler so there is a little mixing and matching here)
thus if a ruler for Libra is ever determined, it would have qualities of the open, confrontational 180 degree opposition aspect. But since the so called "hard aspects" are represented by female planets, Libra though an extroverted air sign, would have a feminine ruler.
i have been looking at Eris transits in opposition to natal planets in some charts, and found it prominant in relationship issues, though admittedly these charts all involved Eris opposing planets in Libra. T.S Eliot had his wife Vivien confined to a mental institution for the remainder of her life in 1938 when Eris opposed his natal sun in Libra, so ending their troubled marriage together. Pablo Picasso, a Scorpio, had a happy extra-marital affair in the late 1930's when Eris transited in opposition to his natal Venus in Libra. (the much less exceptional "el xarko" character, student of astrology and mispeller of the word "geneious", had no affairs, happy or otherwise, when Eris transited in opposition to his own natal Venus in Libra, so you people out there watching out on Eris transits to your man's or woman's chart, don't despair. (el xarko did become a big nerd during this time though, ranting about Plato and hypercubes, and couldn't get a date for years- on a spirit trip instead he claims)
Marilyn vos Savant has a natal Neptune/Eris opposition within arc minutes of exactitude. She reportedly has the highest IQ ever measured, which can't be said of the other poor slobs born around the same time as her. She is also funloving and pretty, and would make a great poster child for Erisians, except that her Leonine pride probably prevents her from believing in astrology.
anyway, i'm guessing that in the opposition aspect will be many clues for astrologers wishing to get a handle on Eris in charts, and her meaning in our lives, inner and outer. Hail Eris!