Erinyes

The Planescape Erinyes.

The Erinyes (singular Erinys) or Furies were a trinity of lesser goddesses in Greco-Roman mythology, Alecto, Megarea, and Tisiphone, who governed Vengeance & Retribution, and would later become figures of justice. In either case, they were empowered to punish the wicked, especially oathbreakers. Ancient Greek culture often venerated the "natural order" of things; in such an order, word was bond, and people were expected to demonstrate as much and show respect to their gods, their parents, their elders, and their guests. Anyone who went back on their word or otherwise proved to be impious or sacrilegious was considered a scumbag of the highest order, and the Erinyes were the trio called upon to vent their righteous fury upon the offender.

Dungeons & Dragons

In Dungeons & Dragons, Erinyes and Furies are two different monsters.

Erinyes

These Erinyes have absolutely nothing to do with the Greco-Roman story. They're the Devil equivalent of the Succubus, being attractive fiends who resemble fallen - but still gorgeous - angels. Different attitudes to account for the difference between Baatezu and Tanar'ri, but still the same basic concept. 3E mentions that Erinyes can look like men, but this never took off, and there's no single depiction of one as male.

The exception is in 4th edition, where succubi switched sides to the devils; now, Erinyes (given a more bestial makeover) were wrathful champions of hell and essentially diabolic amazons.

The "wrathful champions" bit is kept in 5e, but they are once again in pretty forms, mainly to pass themselves off as angles to the misinformed and obliviously pious to catch them later off guard with their devilish ferocity or trick them to Hell's ends.

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  1e
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  2e
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  3e
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  Erinyes got a more warlike makeover in 4e, now that they were no longer trying to compete with the Succubus.
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  5e went right back to being a pretty devil, though they are now warriors and are no longer focused on seduction.

Furies

The Furies of Ravenloft are far more faithful to the actual mythology, consisting of three fiend-like entities who resemble harpies. But, as Ravenloft is the biggest Fuck YOu Players setting in D&D, they are twisted around in one key detail: whereas the mythological Furies punished the wicked, these furies are blights upon the goodly, as their charge is to prevent any evil soul in Ravenloft from trying to seek redemption. As in, they will publically rip you to pieces if you refuse to continue being an evil asshole.

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Pathfinder

Erinyes, as OGL monsters, were included in Pathfinder without much modification. It got a Combat Reflexes as a consequence of PF's improved feat rate, it has slightly higher HP from outsider going from d8 HD to d10, and its strength is one higher in exchange for its dex being one lower (a strict upgrade as both were odd scores), and its rope works slightly differently.

Fluff-wise there's one major change in that Asmodeus is sexist in regards to devils because female devils like Erinyes, are different species from males and are statistically weaker than most male devil types. This seems to have been omitted from Second Edition, as now Erinyes are stated to be able to take on any gender. This is likely due to Paizo's more "progressive" stance that they have been taking for Second Edition, and they probably decided to axe the sexist aspects... of hell.

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