Makes it sound like these two polarity partners Libra (Yang to Scorpio's Yin) operate as a unit: This imagery has them as two parts of the same animal. So if the constellations as pictured by the Ancients are given top priority, only 11 are being used; it's the sign Librio!
In some ways, I feel like the signs of Virgo, Libra and Scorpio are all connected. That's not to say that they're the same sign...
But, like, Virgo is a perfectionist and Libra is a perfectionist too in it's own way. Libra is very idealistic. Everything is either "too this" or "too that", which can cause them to be critical in a different way than Virgo is. Often, Libra is afraid to come to a decision because they want their decision to be the
right one.
Libra and Scorpio are both relationship signs in their own way. I was born on the "cusp" and personally, I don't believe in cusps because objectively speaking, your sign is either in one sign or the other but if we're going by cookbook sun sign astrology, the standard description of my "cusp" sign fits me a lot better than the standard description of Sun in Libra (or the standard description of Sun in Scorpio) and this is going by what other people have said about me (people in real life who probably aren't as into astrology). It's probably because, if we're taking the whole chart into account, Scorpio is my dominant sign. As an archetype though, I relate more to Libra, but more in a Saturnian way (it's exaltation) than a Venusian way. I relate more to the lawyer/judge archetype, and the Justice tarot card, than I do the flirtatious beauty-obsessed seductress. I sometimes
wish I was that flirtatious, beautiful seductress, but nope.
All signs contradict the sign before it and in many ways, Scorpio definitely contradicts Libra. At it's best, Libra is unity and cooperation. At it's worst, (obviously not in the context of sex) Scorpio is separation and competition. Libra represents more of a "peace and love, why can't we just all get along?" liberal hippie archetype, and Scorpio is more divisive and polarizing. "That airy fairy **** doesn't work, take some real action." As we all know, Libra can get too caught up in pleasing others at the expense of themselves, and Scorpio can get so caught up in their own emotions and their desire for power that they don't mind stepping on others (or risking anything, really) in order to get what they want.
But honestly, I think this combination can be harmonic in a way...and not just because Libra is "charming" and "flirtatious" and Scorpio is "sexy" and "mesmerizing". I feel like Libra's impartiality and ability to see all sides of things combined with the investigative, truth-seeking qualities of Scorpio can be very beneficial. In order to really stand for justice, you have to have some will power!
I feel like this combination can make for a good therapist. Libra cares about other people, but isn't always good at reading them. It's an air sign, and they can sometimes be a little air-headed. Naive. Scorpio is excellent at reading people but doesn't always care about them. Libra's diplomacy and Scorpio's ability to keep secrets are also good skills to have.
As JupiterAsc pointed out, "Libra" used to be the claws of the scorpion (gaining power through diplomacy and a peaceful front? using charm as a way to get in someone's pants?). In Rome, Libra was said to be the scales of Astraea, associated with the sign of Virgo. So, Libra has it's connection with both signs in that sense, and Virgo and Scorpio have a connection as well... those M glyphs. Virgo's glyph, ♍, represents the female sex organ, while Scorpio's glyph, ♏ represents the male sex organ... Libra, ♎, being the balance, or "marriage" between these two.
Virgo and Scorpio have similar personality traits as well, both being discriminatory, quiet and slow to trust, though this might have more to do with them being in the harmonious elements of water and earth.