The Ahrimanes are a rare, all-female bloodline of Kindred that originally existed during the Dark Ages, headed by a woman called Ádísa. Sometime during the Long Night, Ádísa and her bloodline were lost and subsumed into Clan Gangrel. Centuries later, the bloodline was unknowingly resurrected by a woman called Muricia. Since then, the Ahrimanes roam the night again, albeit under a different guise and leader.
There have been two "strains", so to speak, of Ahrimanes. One existed during the Dark Ages, and one is a recent development. It is unknown if members of the previous strain have survived into the Final Nights via means of Torpor or similar ways.
The story of the Ahrimanes, as they would tell it, begins with Ádísa, a Valkyrje and daughter of Freyja, the Norse goddess. Traveling far and wide, Ádísa drew the attention of a Persian king named Ahriman. The king commanded Ádísa to fight for him in his army, but she refused to be tied so. Furious, Ahriman sent his forces to subdue Ádísa and, whilst she was exceedingly powerful, even the Valkyrje could not stand against such overwhelming forces. Unwilling to submit under any circumstances, Ádísa remained standing until a warrior slew her on the third day.
When Freyja came to take her daughter to Fólkvangr, Ádísa refused. She did not begrudge the warrior who had slain her, since he had fairly bested her, but she loathed the king for his presumption and waging war against a single woman. Seeing her daughter's distress, Freyja consented to hide Ádísa from the other gods for three nights, though not days, so she might seek her revenge.
The first night, Ahriman and his court fled from Ádísa in great carriages and ships. However, Ádísa's mother had taught her daughter to speak with the animals of the earth when she was young, and they told Ádísa where the king had gone. The second night, even more fearful of Ádísa, Ahriman slew all animals around him so they could not betray him. But Ádísa was not her mother's little girl anymore; she was dead now and could speak to the spirits of animals.
The third night, Ádísa arrived at Ahriman's castle where the king had bricked up all doors and windows. Enraged by his cowardice, Ádísa tore the castle apart with her bare hands until she found the king. As she killed him, she took his name from him as punishment so he would wander forever lost in the afterlife.
When Freyja returned to take Ádísa with her, the Vakyrje still refused. Ádísa's own vengeance was done, but other women had been wronged too, and she would support them. She gathered them under the name Ahrimanes, which was hers by right of conquest, as a reminder of her purpose. Ádísa walked the night as their leader until she and her bloodline were lost during the Long Night.
The Ahrimanes returned, in a fashion, centuries later when a Cainite named Muricia sought independence from her clan. Upon arriving on the new continent, Gangrel of both the Camarilla and Sabbat went into the southern wilderness, encountering a number of native tribes. Many of these Gangrel set up their havens near villages of these people, preying upon the villagers and defending them from the white man's intrusion.
Muricia studied the powers of the local shamans and, calling upon arcane powers to alter her vitae, unknowingly sparked a lingering trace of Ádísa's infamous independence inside her. When Muricia utilized the thaumaturgic powers of the native shamans, she effectively separated herself from her clan and her blood forever altered. She soon combined the spiritual magic of the shaman with her own Gangrel powers, giving her an unusual edge over most of her type. She used this magic to break her Vinculum with her sire, not wanting to get caught up in the constant warfare between two rival leaders of the Sabbat Gangrel.
From then on, the Ahrimanes roamed the night again, albeit under a different guise and leader. In modern times, Ahrimanes were simply known as a Sabbat-affiliated bloodline that shared an unusual bond with spirits, operating mainly in the southern United States. They were seen as an offshoot of the Gangrel antitribu by the other clans.
The Ahrimanes were never numerous, and although they remained nominally allied with the Sabbat, Muricia made it quite clear that they were to be left alone. This isolation may have doomed them, however. In the late 1990s, all contact with the Cats ceased.
Investigators found, sometime later, that their havens were empty, and no one has heard from them since. Most Sabbat believe that the Ahrimanes were destroyed, but concede that it is possible that Muricia might have led her line on a spiritual pilgrimage somewhere out of the Kindred's reach.
In the Dark Ages, the Valkyrjer were surprisingly well-organized for a nomadic group spread out over Europe's coastlines. An Ahrimane usually learned a runic script from her sire not intended for outsiders, so she could leave messages for other Ahrimanes. These symbols conveyed only basic meanings such as "hostile Cainites" or "good hunting", but it was enough to give a small edge to an Ahrimane entering a new territory. The average Ahrimane did not always share a common goal or leader with the rest of the bloodline, but an Ahrimane would usually stand with her sisters.
In the Final Nights, Muricia tried to create others like herself, but soon discovered she could not, as her vitae was infertile. She learned she could choose existing Gangrel and, using the same ritual the shamans used on her, make them like her. Because of this, all modern Ahrimanes were Gangrel before they became Ahrimanes. In addition, Muricia allowed only females to join her brood, believing men to be inferior and the reason for most conflict.
Since all of these "new" Ahrimanes effectively had the same "sire", they were all beholden to Muricia. She did not attempt to control or rule her creations, but did keep tabs on them and helped them develop their powers of Spiritus. The bloodline was fairly tight-knit, as vampire "families" go, and threatening one Ahrimane generally meant battling several.
In the Dark Ages, an Ahrimane's existence was usually nomadic and she quickly learned to make daytime shelters inside fallen trees or small caverns. An Ahrimane did not generally thrive in cities. If she did find herself there, she would seek out abandoned locales to make her haven.
An Ahrimane usually did not discriminate when it came to prey, feeding on men, women, and children alike. Only breastfeeding mothers, infants, and pregnant women seemed to be excluded as Ahrimane prey, perhaps as deference to Freyja, who is also the goddess of fertility.
In the modern day and age, the Ahrimanes are more of an artificial bloodline. All Ahrimanes must renounce their former clan before they are accepted into the bloodline.
In the Dark Ages, Ádísa's bloodline consisted of women only. There were some stories, far and few between, of an Ahrimane falling in love with a man and Embracing him, and these usually ended with the renegade couple hunted down and killed. Ádísa's gift was not for men.
Women whose bodies did not match their spirit were accepted, however, Ádísa favoring the spirit in these cases. Following the Embrace, they would be treated like any other Ahrimane.
An Ahrimane sire seeks out strong, independent women for the Embrace. Knowing how to hunt and fight is a bonus, but a sire knows that skills are more easily taught than attitude. Social standing does not matter to her, as a nomadic lifestyle usually renders lofty positions moot.
However, all modern Ahrimanes were Gangrel before their magical transformation. As such, their backgrounds varied just as much as their parent clan. The sort of Gangrel who became an Ahrimane was female, usually non-white, and often frustrated by the situation in her sect or city.
The Ahrimanes were introduced in the Second Edition Storytellers Handbook to the Sabbat, but never updated in the Revised Edition. They did later receive a writeup in Vampire: The Masquerade 20th Anniversary Edition.
Clanbook: Gangrel Revised gives a brief writeup of the bloodline and how they may have made new members; however, they are also listed as all missing and suspected destroyed. This book suggests to use Thaumaturgy to simulate their Discipline of Spiritus.
In VTDA20. the Ahrimanes were given an expanded background with roots in medieval Scandinavia, with Muricia having only rediscovered the bloodline, rather than inventing it.