In Curse Of Strahd, the prophecy came literally true, as Shakti followed a vision of Ylyana's into Barovia. She was killed in Berez by the witch Baba Lysaga, but with the blessing of Mother Night, Jaghr reached out to her, and shielded her soul from being consumed by Vampyr.
A Human born to a group of feral forest-folk south of the Wealdshield, Jaghr was taught Ranger skills as a youth. On his first solo mission as a teenager, he was bitten by a Werewolf and contracted Lycanthropy in the northern Sea of Trees. To ensure he was not a danger to his small tribe, Jaghr sought the help of the druids of the Astralwood, hearing of their abilities and acceptance. He found a home in the Astralwood Enclave, beginning as a Speaker of the Wood due to his minor skills in divination. He would spend time between his nomadic tribe and the permanent enclave, using his tracking skills to always find his way back to his family.
His love for nature and wonder of the Lake of Telyth lead him to grow close to the Archdruid Ylyana the Starseer, the oldest living member of the Astralwood Enclave. They lived together a short time and had a child, Shakti of the Wildhunt, but their love was tumultuous. Though they were attracted to each other through their mutual worship of Telyth, Ylyana was unpredictable, and her attention for Jaghr waxed and waned. Similarly, Jaghr acted the same as both a partner and father, often disappearing from his home and responsibilities for weeks at a time.
The Guardian of the Wood and leader of the Keepers of the Forest, Arbor the Woodswatcher had always been at odds with Jaghr. The lycanthrope's emotions heightened during the full moon, even when aided by druidic magic, and the two fought under the light of the moon. Rumors said that Arbor slayed Jaghr in the Vanishing Grove, but the truth of the matter was thought to be unknown to all but the Paladin himself. Jaghr was reported dead, though his body was nowhere to be found.
In actuality, even Arbor had not known what happened to Jaghr, as encroaching mists enveloped them when they fought in the grove. Jaghr was sent to Barovia, to an area divorced from time called Yester Hill. With no idea where he was in the world, he turned to fortune. A Tarokka Deck reading from a traveling Vistani seer foretold a prophecy: he would fight a battle at the Hill and then would sire a great pack, developing a legacy as a legendary werewolf. To protect his future children, he would have to leave his only daughter behind.
This prophecy radically altered Jaghr's beliefs. He was permanently trapped in the valley, as its mists would not allow him to leave. Confined in a different world without the warm druidic magics that allayed his temperament, Jaghr embraced his feral side. He allied with the hill-folk who worshipped the Lady of the Mountain and met the leader of the people, the Blood Chief Kavan. The two developed an incredibly close kinship, and Kavan convinced Jaghr to train his people in the ways of hunting and fighting, as the forests were being overrun with the troops of Strahd von Zarovich.
The wolf-man assisted in training them to fight for the future of the valley. Their effort was ultimately for naught, however; they lost the Battle of Yester Hill, and Kavan was killed in the fight. A wounded Jaghr took his Blood Spear and retreated north to save the lives of those he could. After they were routed, he had escaped with many hill-folk, heading past Zachodgrad to the Balinok Mountains.
There, he infected others and sired many other children, developing a community of both forest-folk and native Barovians such as his subchief Ladislau Krezkov. Becoming known as the "Wolf-Father", he reintroduced widespread lycanthropy in Barovia, and his tribe would eventually establish themselves at the Werewolf Den. He also espoused the ideas of Telyth, who overlapped with the Barovian idea of "Mother Night", and created a lineage that would pass all the way down to the likes of Kiril Stoyanovich and Helwa.
Jaghr was smote by Saint Markovia at Saint Markovia's Pool, in a glorious battle that temporarily brought the sun back to Barovia. Destroyed by the light of Thestus and having lived an unfulfilled dual-life, Telyth took pity on him, shielding his spirit from Vampyr's consumption. For hundreds of years, his spirit remained in the Werewolf Den, tending to the shrine of Mother Night and overlooking his descendants.